Bleach: Kusajishi Yachiru - She is by far the coolest I think. She is just so bad ass and doesn't show it. As she chills on Zaraki Kenpachi's back. Talk about straight up bad ass.
DB: I would have to say Majin Buu. He's just straight up human bad ass because of his multi-personality. Good-Evil-Kid-Super. Come on, it can't get any better.