Smash 64: I don't really have a main in this game since I don't really play it very often. However, if I was going to choose one character, it would have to be fox.
Melee: The characters that I prefer to play in this one are Ganondorf and Fox. There's nothing quite like crushing the hopes and dreams of your opponent by either shine spiking them offstage as fox or just plain stomping them into oblivion as Ganondorf.
Brawl: Samus and jigglypuff. I've only just recently begun to play this game often after abandoning it for Project M about a year or two ago.
Project M: (Yes, I know that this is a mod, but it might as well be counted as a game honestly.) Anyway, I mainly use Shiek, Snake, and fox in PM.
Smash 4: Don't have a main in this one since I don't even play it.