Just a note; I've just gotten into MLP: FIM so ask me how you became an brony, began watching the show, etc. (I've gotten into MLP when reading Stardust's "AJBS". Since then, I've liked MLP.)
My favourite Pokémon is probably Charizard or Pikachu. Either of them are good. Though, Alain's Charizard battled the Weather Trio. I'll go with Charizard (not because it's cool, though)