Tyrannitar. What's cooler than a massive dinosaur covered in rock that storms about crunching and stomping everything in it's path? That's right, not much. It's biggest threat is probably Breloom, due to the MASSIVE type advantage, but that can easily be solved by equiping T.Tar with a chesto berry to counter Sporepunch, and an Aerial Ace to tackle Breloom. With mediocre defence, Breloom would find it hard to tolerate an attack it's super-weak to in the first place, and AA's always-hit-first would make up for T.Tar's lack of speed.
Ahem. And I can't say I like those other fellas much.