I was flipping through some manga/comics I have and just thought of the question, which is my favourite anime outfit. Mine is: Might Guy's (from Naruto) tights. There is an episode he gives Naruto the tights which Rock Lee and Might wears, and I just found it funny. LOL. But on the cool-side, it would be maybe the emo Ulqiorra's outfit.
Grimmjow has a nice style.. Ichigo when he have his bankai.. and also Asakura Yohs outfit that he gets in episode 15 or so..