My White 2 MVP was my Cinccino. I caught the Skill Link one in the Hidden Grotto, and he was an absolute beast. His moveset was Bullet Seed, Tail Slap, Rock Blast, and Sing, and he could take out most things in one or two turns.
My Black 2 MVP was my Garbodor. She was actually my worst Pokemon at first, but then I taught her Toxic and Venoshock, and she began to wreck stuff with just those two moves. She also knew Body Slam and Sludge Bomb, but she mostly just used those to finish what Toxic and Venoshock started.