King Ghidorah

With an idea like that, I'm surprise someone hasn't spriteswapped Hiperhazz's Kyurem.

Guess it's thankfully not popular enough yet :)

you mean the one who goes Black/White when you beat him the first time, then goes OP when you beat him to about 75% of his life?

that's OP at its finest.

my idea of the Charizard though, would be where you just press a simple button (maybe X/Y for fittingness' sake) and Charizard turns into one of two Megas throughout the battle.

I also wouldn't mind seeing a Blastoise who can go Mega, and Venusaur who can go Mega but ehhh....I'd make Charizard my most wanted.

someone should make a Charizard character that can (permanently) switch between either Mega Charizard Y or Mega Charizard X.

I would, but the spriting would be simply godawful.