even though it's only in bw, i think that politoed deserves a mention. it was mediocre at best in every other generation--actually, if it wasn't for drizzle, it would be in ru, max this gen--but rain is so utterly metagame defining that it deserves to be on here somewhere. if drizzle didn't exist in ou, ou would be unrecognizable at the moment. so many of the top pokemon in the meta rely or at least benefit from rain-torn t, keldeo, ferrothorn, scizor, tentacruel, dragonite, rotom w, the list goes on. in short, the current metagame would barely exist without its rain. it's the most important pokemon of this generation, no competition.