Wanted to improve on this set skiddle, since I just recommended it to Chris is Me for his Empoleon team. I've been using it for months and thing this set may even be more useful than the Choice Specs set, as I haven't seen a Choice Specs Heatran in MONTHS! Requesting this to be moved up...
[SET]
name: Bait-Tran
move 1: Stealth Rock
move 2: Explosion
move 3: Fire Blast / Flamethrower
move 4: Earth Power
item: Life Orb
nature: Hasty
Ivs: 30 SpD
evs: 56 Atk / 200 SpA / 252 Spe
[SET COMMENTS]
<p> This set is nearly guarenteed to remove your opponent's main Heatran counter, which is usually a bulky Water type like Vaporeon, or everyone's favorite obese nurse. The idea is to play this like a regular Heatran, coming in on a pokemon that you immediately threaten and force out. Use Stealth Rock on the switch to benefit your team and scout for the counter while concealing Life Orb recoil. Now you have two options; you can blow up immediately, or switch out to lure your opponent into a false sense of security. Next time Heatran enters the battle, simply explode on the incoming Blissey / Bulky Water, thus clearing the way for a special sweeper or something that hates bulky Waters. When engaging stall teams, it is best to note that they play more conservatively and are more likely to protect with their Blisseys or Vaporeons on turn one, so predict accordingly.</p>
<p> The Attack EVs and Life Orb allow you to always OHKO Bold 188 HP / Max Def Vaporeon, along with Max Def Blissey 100% of the time. Otherwise, simply play this as a standard attacking Heatran. It has enough speed to outrun most Gyarados also if they show up, and will OHKO offensive varients regardless of Intimidate.</p>
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Listed IV combination for legality's sake, since I've been using it forever.