[hi no ken Jebus]

Ace obviously, Whitebeard, Mihawk, Shanks, and the ever lovable rascal Buggy. Ace your narcoleptic cowboy, Whitebeard 2nd most powerful pirate after ol' Gol D., Mihawk #1 swordsman in the world, Shanks the baddest one arm badass this side of the Grand Line, and Buggy because I love that clown.

But since the question is favorite character singular, I'll put my money on Shanks he's not feared and well known for nothing.