Nominating Tyrantrum for B+. Rock Head isn't QUITE as good as Contrary, but it sure as hell has a lot more turn 1 power, including 2HKOing Suicune without Rocks.
252+ Atk Life Orb Tyrantrum Head Smash vs. 252 HP / 252+ Def Suicune: 218-257 (53.9 - 63.6%) -- guaranteed 2HKO after Leftovers recovery
The Rock Polish set is an insanely deadly cleaner, while Hone Claws could break stall in half. It also has a very interesting typing, letting it eat up every Fire-type attack in the tier. With a Lum Berry, it can even check Entei. Unfortunately, every Fire-type also has a move that can break through it (Close Combat, Iron Head, Bulldoze, Earthquake, Superpower, Shadow Ball), but if you can get around those then you shouldn't be hurting too much. It also is a great Flying check, basically shutting down Crobat completely, forcing it to U-turn out, since Head Smash OHKOs after Rocks even if it tries to Roost. It's 2HKO'd by Mega Pidgeot's Hurricane, but assuming you switch in on literally any other move you're pretty safe to just break it in two with Head Smash. Its movepool isn't too terribly deep, but it does get Stealth Rock, and with a meaty base 119 Defense, it's certainly capable of eating up some physical hits. I could even see it being run as a dedicated Entei check with Wish and Heal Bell support, given just how stupid fucking hard it hits with Head Smash, sorta like Granbull using its base 120 Attack, only hitting literally more than half-again as hard.
Now, on to why Tyrantrum shouldn't (currently, I've played like four games with it) go any higher: Its bad speed and Special Defense. Base 71 Speed isn't a lot (just ask Honchkrow) and base 59 Special Defense is just sorta laughable. While you should be eating Mega Pidgeot's Hurricane and scaring it right the fuck out, you just get 2HKO'd after Rocks if you aren't running some serious SpDef bulk. Well, actually, SpDef is kinda cool, given how much base Defense you have. I'll get back to that later.
Its speed is really disappointing. Its outsped by a fair number of Scarfers even at +2 if it's Adamant, which it really appreciates for the power. Notable among these are Hydreigon, Salamence, Infernape, and Mienshao, all of whom OHKO with a super-effective STAB move. This is why I'm fully convinced a Dragon Dance set is a waste of time. Even Jolly, you're outsped by a fair number of unboosted Pokemon, and Mega Sceptile pretty much uses you as a punching bag in particular.
Its typing is cool when you're facing down Crobat and Darmanitan, but not so much when you're facing stuff with Steel, Fighting, Ground, Ice, Dragon, or Fairy attacks. Six weaknesses, three of which are hilariously common in UU, is a huge issue given his poor speed.
Closing thoughts: Hone Claws can/will destroy stall, you could even pair it with Heracross as a Crobat switch-in. This works really well since anything that can conceivably switch in on a boosted Head Smash Heracross destroys. A SpDef set or Assault Vest is an option, letting you check Mega Pidgeot more comfortably. Apologies if this started to get really disjointed and bizarre, I got sidetracked and wrote this out over a few hours.
