So I looked around and couldn't find a thread that discussed trapping and its abusers. So I decided to start one.
Trapping is one of those things everyone hates, but at the same time loves. It is, in a nutshell, limiting the switches of your opponent via abilities, moves, or sheer offensive presence. Each of these is viable, and usable competitively, in fact if you don't use it you put yourself at a serious disadvantage. Average players can use trapping to stop enemies momentum. Good Players can use it to start their own momentum. Amazing players can win battles with it. So on to the basics.
Trapping in the most basic form is stopping a switch. This first time this was possible was way back in Gen II, with the introduction of the move pursuit. Pursuit itself was a weak and relatively useless move at the time, as the metagame was extremely bulky. Curselax was king, and if anything tried to get in its way they were completely bowled over. This lead to a very stall orientated metagame and pursuit was more or less left alone.
Then along came Gen III, an with it the introduction of abilities. These abilities were relatively widespread, with the exception of a couple. One of these unique abilities was Shadow Tag, and the pokemon that got it was Wobbuffet. Now Wobbuffet doesn't have much going for it. It has a movepool almost as bad as Unknowns, and its only good stat was its HP. Nevertheless with the introduction of Shadow Tag to its arsenal Wobbuffet became a terror like no other. It was uncounterable. Instantly its was banned to Ubers never to see the light of OU again.... Until Gen V. The other trapping ability was also made at this time, Arena Trap. Also sparsely distributed its abusers were much easier to deal with. Also the fact that Flying Types and levitators could switch out with impudence hurt its overall performance. The final trapping ability also appeared in Gen III, Magnet Pull. Even more limited in what it could trap (Steel Types only), Magnet pull saw distribution among only a few pokemon.
Gen IV came and went with little added to trapping, except for one move, U-Turn. Not a move that prevents switching or hurts pokemon when they switch, instead a move that traps your opponent by limiting his options. Scizor ruled in a large part due to this. A counter was no longer able to counter if the enemy wasn't there. Used correctly this could have devastating effects on your opponents team. Also Magnet Pull gained more popularity with the rise of dragon and their counters, Steel types. Magnezone also had an impact in this rise.
Then came Gen V. No new trapping abilities came out, only Volt switch and some tier changes. Wobbuffet was now out of Ubers. The menace that had dwelt among gods only due to his ability was set free on an unpredicting metagame. But he had been hurt. His sparse movepool had taken a beating in the form of a nerf for Encore, the premier move of his movepool. No Longer did he have a blessed 5 turns to do whatever he wanted, he was now limited to 3. And the metagame had evolved. His gargantuan HP stat was no longer enough to keep him alive. And the art of trapping was lost in the darkness...
Or was it?
Pursuit is perhaps one of the most useful moves in the current Metagame. Latios and Latias also fell from grace and joined us in OU. Fighting types invaded the metagame, and with them came powerful Psychics, pokemon whose mind power is enough to twist the very fabric of reality. And Weather wars began. Any residual damage is useful, and the ability to cause harm to a pokemon trying to run away is useful to say the least.
Now without further ado on to the Trappers.
Dugtrio
Ground
Base Stats:
HP - 35
Atk - 80
Def - 50
Sp.Atk - 50
Sp.Def - 70
Spe - 120
Dugtrio has always been an unorthodox choice for an OU team. As the only fully-evolved user of Arena Trap, Dugtrio is a fantastic revenge killer. Dugtrio also has blazing Speed and a passable offensive movepool. However, while its lackluster base Attack can be improved by Choice Band and Life Orb, it still lacks enough muscle to push through most healthy enemies. Furthermore, its defenses are certainly not capable of handling much more than a weak priority attack, and its high Speed can be overcome by opposing Choice Scarf users. In addition, Dugtrio is almost begging to be trapped by Pursuit. In this generation, Dugtrio welcomes the coming of many grounded competitive threats. Unfortunately, it quickly realizes that their defenses are higher, as well. It also finds that a Ground-type STAB is less reliable than ever due to the introduction of Air Balloon. Luckily, with the introduction of valuable sandstorm sweepers, the ubiquitous Tyranitar becomes more and more important to remove – a task which Dugtrio is eager to fulfill.
(Credited to analysis page)
As his analysis description describes Dugtrio pretty well I will leave it there.
Magneton/Magnezone
Electric/Steel
Base Stats:
HP - 50/HP - 70
Atk - 60/Atk - 70
Def - 95/Def - 115
Sp.Atk - 120/Sp.Atk - 130
Sp.Def - 70/Sp.Def - 90
Spe - 70/Spe - 60
Although Magnezone hasn't improved much in the 5th Generation, its unique ability to trap Steel-types along with its numerous resistances and respectable defensive stats give it a place as a top-tier OU Pokemon. While Magnezone's Speed is below average—even being outsped by its predecessor, Magneton, it more than compensates with its reliability and power. If your team has trouble with Steel-types such as Scizor, Forretress, and Ferrothorn, then there is no reason not to consider Magnezone for a spot on your team.
(Credited to analysis page)
Magneton and Magnezone play an important role in todays metagame. The ability to trap and remove steel types is invaluable to Dragons, and a good strategy overall. With 6 of the top 15 pokemon being steel type Magnezone/ton can be a valuable asset to any team needing steels removed. Magnezone has decent bulk and higher Sp.Atk allowing it to effectively counter most steel types. Magneton on the other hand has Higher spped and better defenses with an Eviolite. They both perform similar roles and the choice between them is up to your preference.
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Trapping is one of those things everyone hates, but at the same time loves. It is, in a nutshell, limiting the switches of your opponent via abilities, moves, or sheer offensive presence. Each of these is viable, and usable competitively, in fact if you don't use it you put yourself at a serious disadvantage. Average players can use trapping to stop enemies momentum. Good Players can use it to start their own momentum. Amazing players can win battles with it. So on to the basics.
Trapping in the most basic form is stopping a switch. This first time this was possible was way back in Gen II, with the introduction of the move pursuit. Pursuit itself was a weak and relatively useless move at the time, as the metagame was extremely bulky. Curselax was king, and if anything tried to get in its way they were completely bowled over. This lead to a very stall orientated metagame and pursuit was more or less left alone.
Then along came Gen III, an with it the introduction of abilities. These abilities were relatively widespread, with the exception of a couple. One of these unique abilities was Shadow Tag, and the pokemon that got it was Wobbuffet. Now Wobbuffet doesn't have much going for it. It has a movepool almost as bad as Unknowns, and its only good stat was its HP. Nevertheless with the introduction of Shadow Tag to its arsenal Wobbuffet became a terror like no other. It was uncounterable. Instantly its was banned to Ubers never to see the light of OU again.... Until Gen V. The other trapping ability was also made at this time, Arena Trap. Also sparsely distributed its abusers were much easier to deal with. Also the fact that Flying Types and levitators could switch out with impudence hurt its overall performance. The final trapping ability also appeared in Gen III, Magnet Pull. Even more limited in what it could trap (Steel Types only), Magnet pull saw distribution among only a few pokemon.
Gen IV came and went with little added to trapping, except for one move, U-Turn. Not a move that prevents switching or hurts pokemon when they switch, instead a move that traps your opponent by limiting his options. Scizor ruled in a large part due to this. A counter was no longer able to counter if the enemy wasn't there. Used correctly this could have devastating effects on your opponents team. Also Magnet Pull gained more popularity with the rise of dragon and their counters, Steel types. Magnezone also had an impact in this rise.
Then came Gen V. No new trapping abilities came out, only Volt switch and some tier changes. Wobbuffet was now out of Ubers. The menace that had dwelt among gods only due to his ability was set free on an unpredicting metagame. But he had been hurt. His sparse movepool had taken a beating in the form of a nerf for Encore, the premier move of his movepool. No Longer did he have a blessed 5 turns to do whatever he wanted, he was now limited to 3. And the metagame had evolved. His gargantuan HP stat was no longer enough to keep him alive. And the art of trapping was lost in the darkness...
Or was it?
Pursuit is perhaps one of the most useful moves in the current Metagame. Latios and Latias also fell from grace and joined us in OU. Fighting types invaded the metagame, and with them came powerful Psychics, pokemon whose mind power is enough to twist the very fabric of reality. And Weather wars began. Any residual damage is useful, and the ability to cause harm to a pokemon trying to run away is useful to say the least.
Now without further ado on to the Trappers.
Abilities
Wobbuffet
Psychic
Base Stats:
HP - 190
Atk - 33
Def - 58
Sp. Atk - 33
Sp. Def - 58
Spe - 33
At first glance, Wobbuffet seems to be horrible due to having a movepool consisting of literally 8 moves and horrendous stats in everything but HP. However, Wobbuffet has the ability Shadow Tag, which turns it into a serious threat. Wobbuffet's movepool also complements its ability perfectly, consisting of moves such as Encore, Mirror Coat, and Counter, allowing Wobbuffet to almost always guarantee a KO or a free setup for a teammate. Wobbuffet's stats are actually a bit of a blessing, as its enormous HP and bad defenses make Counter and Mirror Coat hit for tons of damage. Wobbuffet even gets Tickle to round out its Shadow Tag-abusing movepool.
Sadly, Wobbuffet has to contend with problems both new and old in the 5th generation. Wobbuffet still lacks any form of recovery, which is unfortunate because it's hit by every entry hazard and all forms of damaging weather. Wobbuffet is also severely crippled by Taunt, often being rendered helpless while the opponent sets up. Perhaps the most debilitating problem is the nerf Encore received in this generation, only lasting 3 turns instead of 4-8 turns, making the already low PP of Encore even more of a problem. The general power of attacks has also increased dramatically, cutting short the number of times Wobbuffet can switch in and knock out the opponent. Despite these flaws, Wobbuffet remains a dangerous threat which every team should watch out for.
(Credited to analysis page)
The core of trapping. Wobbuffet's ability to trap and kill pokemon is second to none. Wobbuffet was hit hard in the generation shift though and has lost a lot of it utility that it once had. If you are looking for a pokemon that can reliable kill almost anything this is your go to guy. Just be aware that his utility outside of the is zero. After he kills an opponent good old Wobb is worn out and can generally only take 1 more hit. 
Wobbuffet
Psychic
Base Stats:
HP - 190
Atk - 33
Def - 58
Sp. Atk - 33
Sp. Def - 58
Spe - 33
At first glance, Wobbuffet seems to be horrible due to having a movepool consisting of literally 8 moves and horrendous stats in everything but HP. However, Wobbuffet has the ability Shadow Tag, which turns it into a serious threat. Wobbuffet's movepool also complements its ability perfectly, consisting of moves such as Encore, Mirror Coat, and Counter, allowing Wobbuffet to almost always guarantee a KO or a free setup for a teammate. Wobbuffet's stats are actually a bit of a blessing, as its enormous HP and bad defenses make Counter and Mirror Coat hit for tons of damage. Wobbuffet even gets Tickle to round out its Shadow Tag-abusing movepool.
Sadly, Wobbuffet has to contend with problems both new and old in the 5th generation. Wobbuffet still lacks any form of recovery, which is unfortunate because it's hit by every entry hazard and all forms of damaging weather. Wobbuffet is also severely crippled by Taunt, often being rendered helpless while the opponent sets up. Perhaps the most debilitating problem is the nerf Encore received in this generation, only lasting 3 turns instead of 4-8 turns, making the already low PP of Encore even more of a problem. The general power of attacks has also increased dramatically, cutting short the number of times Wobbuffet can switch in and knock out the opponent. Despite these flaws, Wobbuffet remains a dangerous threat which every team should watch out for.
(Credited to analysis page)
Dugtrio
Ground
Base Stats:
HP - 35
Atk - 80
Def - 50
Sp.Atk - 50
Sp.Def - 70
Spe - 120
Dugtrio has always been an unorthodox choice for an OU team. As the only fully-evolved user of Arena Trap, Dugtrio is a fantastic revenge killer. Dugtrio also has blazing Speed and a passable offensive movepool. However, while its lackluster base Attack can be improved by Choice Band and Life Orb, it still lacks enough muscle to push through most healthy enemies. Furthermore, its defenses are certainly not capable of handling much more than a weak priority attack, and its high Speed can be overcome by opposing Choice Scarf users. In addition, Dugtrio is almost begging to be trapped by Pursuit. In this generation, Dugtrio welcomes the coming of many grounded competitive threats. Unfortunately, it quickly realizes that their defenses are higher, as well. It also finds that a Ground-type STAB is less reliable than ever due to the introduction of Air Balloon. Luckily, with the introduction of valuable sandstorm sweepers, the ubiquitous Tyranitar becomes more and more important to remove – a task which Dugtrio is eager to fulfill.
(Credited to analysis page)
As his analysis description describes Dugtrio pretty well I will leave it there.
Magneton/Magnezone
Electric/Steel
Base Stats:
HP - 50/HP - 70
Atk - 60/Atk - 70
Def - 95/Def - 115
Sp.Atk - 120/Sp.Atk - 130
Sp.Def - 70/Sp.Def - 90
Spe - 70/Spe - 60
Although Magnezone hasn't improved much in the 5th Generation, its unique ability to trap Steel-types along with its numerous resistances and respectable defensive stats give it a place as a top-tier OU Pokemon. While Magnezone's Speed is below average—even being outsped by its predecessor, Magneton, it more than compensates with its reliability and power. If your team has trouble with Steel-types such as Scizor, Forretress, and Ferrothorn, then there is no reason not to consider Magnezone for a spot on your team.
(Credited to analysis page)
Magneton and Magnezone play an important role in todays metagame. The ability to trap and remove steel types is invaluable to Dragons, and a good strategy overall. With 6 of the top 15 pokemon being steel type Magnezone/ton can be a valuable asset to any team needing steels removed. Magnezone has decent bulk and higher Sp.Atk allowing it to effectively counter most steel types. Magneton on the other hand has Higher spped and better defenses with an Eviolite. They both perform similar roles and the choice between them is up to your preference.
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With the advent of Dream World there will be a few pokemon to gain trapping abilities in the future. Most notable among them is Chandelure a pokemon with a monstrous base 145 Sp.Atk stat.
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Pursuit Users
Pursuit is a move with only 40 base power. But it has an interesting effect, being able to damage pokemon that are switching out. As such it can be invaluable to pick off threats to your team, or just weakened pokemon in general. I'll list some of the better users here.
Tyranitar
Dark/Rock
Base Stats:
HP - 100
Atk - 134
Def - 110
Sp.Atk - 95
Sp.Def - 100
Spe - 61
Tyranitar is perhaps the best known Pursuit user out there. Sporting a base stat total of 600, and an ability that basically provides an Eviolite boost to its Sp.Def, Tyranitar is a monster. Its typing has given it many weaknesses, but it also provides some of its greatest strengths. Rock type allows it to gain a 50% boost to its Sp.Def while in sandstorm, and its ability calls a permanent one to make full use of that. Dark gives it an immunity to Psychic types, while also giving STAB to Pursuit. Tyranitar also boasts of being one of the few full counters to Lati@s.
With its massive bulk Tyranitar is easily able to come in and scare things out, backed by an impressive 134 Base Atk. This allows it to make full use of Pursuit, catching the enemy as the try to get away and causing massive hurt. Unfortunately for Tyranitar it isn't all sand and Psychics running around. Water, fighting, and steel types are at an all time high making life difficult for Tyranitar to stay in for very long. Also Scizor, Tyranitars biggest counter, has relatively high usage, meaning Tyranitar must be careful. A stray U-Turn or Bullet Punch from the metal bug can shorten Tyranitars life very quickly. As such pairing tyranitar with a Steel trapper (Magnezone/ton) can help it lead a happy healthy life, and allow it to pursue victims to the ends of the earth.
Scizor
Bug/Steel
Base Stats:
HP - 70
Atk - 130
Def - 100
Sp.Atk - 55
Sp.Def - 80
Spe - 65
Scizor is the prime example of trapping. It has all the right stuff in all the right places. Priority, U-Turn, Pursuit, and Technician make Scizor a threat to be watched out for. He ruled the roost in Gen IV, and in Gen V he has been in the top 5 consistently so far. With only 1 weakness Scizor can use his typing to his advantage and switch in. After that it is a prediction mind game for your opponent. "Do I switch and take a possible pursuit?", "Do I switch and take a U-Turn to the face?", "Do I stay in and take a 90 Base power priority move?". As each of these questions run through their mind Scizor can pick and choose his move to cause the most damage. Played right Scizor has the ability to completely wreck opposing teams. Used wrong and he becomes set up fodder. Scizor is the epitome of the saying "With great power comes great responsibility."
More will be covered on Scizor's movepool in the Momentum section.
More Pursuit users to be added later.
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Momentum Trapping
To be completed
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I will finish most of this up over time. For right now go ahead and discuss the uses of trapping in competitive play. Feel free to make suggestions too, any that are useful will probably make it up here.
Pursuit Users
Pursuit is a move with only 40 base power. But it has an interesting effect, being able to damage pokemon that are switching out. As such it can be invaluable to pick off threats to your team, or just weakened pokemon in general. I'll list some of the better users here.
Tyranitar
Dark/Rock
Base Stats:
HP - 100
Atk - 134
Def - 110
Sp.Atk - 95
Sp.Def - 100
Spe - 61
Tyranitar is perhaps the best known Pursuit user out there. Sporting a base stat total of 600, and an ability that basically provides an Eviolite boost to its Sp.Def, Tyranitar is a monster. Its typing has given it many weaknesses, but it also provides some of its greatest strengths. Rock type allows it to gain a 50% boost to its Sp.Def while in sandstorm, and its ability calls a permanent one to make full use of that. Dark gives it an immunity to Psychic types, while also giving STAB to Pursuit. Tyranitar also boasts of being one of the few full counters to Lati@s.
With its massive bulk Tyranitar is easily able to come in and scare things out, backed by an impressive 134 Base Atk. This allows it to make full use of Pursuit, catching the enemy as the try to get away and causing massive hurt. Unfortunately for Tyranitar it isn't all sand and Psychics running around. Water, fighting, and steel types are at an all time high making life difficult for Tyranitar to stay in for very long. Also Scizor, Tyranitars biggest counter, has relatively high usage, meaning Tyranitar must be careful. A stray U-Turn or Bullet Punch from the metal bug can shorten Tyranitars life very quickly. As such pairing tyranitar with a Steel trapper (Magnezone/ton) can help it lead a happy healthy life, and allow it to pursue victims to the ends of the earth.
Scizor
Bug/Steel
Base Stats:
HP - 70
Atk - 130
Def - 100
Sp.Atk - 55
Sp.Def - 80
Spe - 65
Scizor is the prime example of trapping. It has all the right stuff in all the right places. Priority, U-Turn, Pursuit, and Technician make Scizor a threat to be watched out for. He ruled the roost in Gen IV, and in Gen V he has been in the top 5 consistently so far. With only 1 weakness Scizor can use his typing to his advantage and switch in. After that it is a prediction mind game for your opponent. "Do I switch and take a possible pursuit?", "Do I switch and take a U-Turn to the face?", "Do I stay in and take a 90 Base power priority move?". As each of these questions run through their mind Scizor can pick and choose his move to cause the most damage. Played right Scizor has the ability to completely wreck opposing teams. Used wrong and he becomes set up fodder. Scizor is the epitome of the saying "With great power comes great responsibility."
More will be covered on Scizor's movepool in the Momentum section.
More Pursuit users to be added later.
<><><><><><><><>
Momentum Trapping
To be completed
<><><><><><><><>
I will finish most of this up over time. For right now go ahead and discuss the uses of trapping in competitive play. Feel free to make suggestions too, any that are useful will probably make it up here.
