Cobalion

Despite UU being a tier filled with Fighting-types, Cobalion has no trouble distinguishing itself from the rest with its unique typing, which grants it a good number of resistances--including a 4x resistance to Stealth Rock and immunity to poison--on top of its excellent physical bulk, good speed, and access to Swords Dance, Calm Mind, and Stealth Rock. On the other hand, it has problems taking special attacks due to its bad Special Defense. Its Steel typing has notable drawbacks in a metagame full of Fighting-type moves, and its offenses can be somewhat lacking. Nonetheless, Cobalion remains a potent threat.