Gin- He's cool and evil. And the fact that his eyes are always closed or really leering kinda gives that evil look. If his eyes were open and he didn't have that creepy joker-style grin I feel like he'd look more innocent.
Grimmjow- When he just comes in and pounds the crap out of Ichigo with his heavy style fighting it's so badass. And he looks so awesome. But his appearance turns sissy once he goes Ressureccion. He gets this tight, white bone suit and a stupid crown thing. Why couldn't they just have like, armor plates on his shoulders and arms and a few scales? Why make him look like a freaking acrobatics instructor? And his hair gets longer, but in a girly way. It hangs down, it doesn't get spiky or anything. I was expecting alot better for his Resurreccion look.
Ichigo- He's cool, but not my number one favorite because 1: He's took freaking weak. He went through all this crap just so he could move at super speed and get super strength, and it's not even equal to 1/2 of Aizen's power. It's ridiculous. And his special attack is so boring. "Look at me I fire a big black blast thingy" yeah that's real nice, but...it just doesn't look strong. I mean, if it was in a bladed shape and it did cutting stuff or something, it'd be cooler.
Yachiru- LOL. She makes the story less bleak and depressing.
Kenpachi- He's a BAMF. He's like the Samuel L. Jackson of Bleach. And he's HAD IT WITH ALL THESE MOTHER****ING SHINIGAMI ON THIS MOTHER****ING PLANE- er, city. >_>
Mayuri Kurotsuchi- He's so crazy and cruel that it's awesome. It's the psychotic evil guy that every anime needs, like Marik in Yugioh or Light from Death Note.