A lot of other stuff has been posted. Although this is about character and not just fighting, here is some shit I love
So my favorite characters are usually the ones who hook me immediately. Luffy, Franky, Zoro, Crocodile, Smoker, Jinbe, Kaido, Yamato... even Krieg.
I dropped the series back at Thriller Bark because of the pacing. When I came back around the end of Impel Down, Zoro's role in Thriller Bark sealed the deal for me. To Luffy's credit first place was neck and neck until then.
Man, I really loved Smoker in the first half of the series. It's not that I'm hung up on power level, but he's just become oddly irrelevant, like a Z fighter, when he seemed set up for so much importance.