1. Hollow Ichigo
When ridiculing the cold Byakuya Kuchiki at the Battle of Sogyoku Hill (that wild shriek 'laughung haha' while attacking was so irritating at worst but because he is one part of the hero it is inspirational too - find it boring with boring heroes do not you)
When going berserk (refer manga) losing his head only god knows what - bullying IRDK what level that Ulquiorra are on that time (ps enlightened me with this) - thus in the end killing IT (maybe some fans would argue this saying Ulq guy still alive - no proof whatsoever).
Versus Zangetsu (anime The Materialisation of Zanpakutou) - I just thought Zangetsu (from the looks - not because he is part of Ichigo) even so experience - is well beaten so easily by this Crazy Went Wild Whitey Ichigo. Sometime he just so make Ichigo looks like a stupid Shinigami.
Some may argue Grimmjow Jaggerjaques is the most Bad Ass guy in Bleach - but he could not submit normal Ichigo to summon that Whitey Guy.
2. Kenpachi Zaraki (KZ)
Nnoitra Jiruga was so (was because he is deceased) Bad Ass - but Mr Bad Ass happen to be more Bad Assed by this guy, KZ was even more bad ass.
Currently was chopping the Big Hollow guy Mr Yammy. There are many Kenpachi moments - where while Bad Assing people he manage to throw few advices too and WOW - How is it possible - DAMN this guy!!!
3. Isshin Kurosaki
I just thought he is a Shinigami (of course a fighter/warrior etc) who likes to tease/ridicules his opponents - a Bad Ass too - he is strong (well no one has ever manage to push Aizen Sosuke to his Shinigami limits not even the Captain Commander). A character when fighting that will disrespect his opponent - for that is inspirational but irritating too. He is an irritating (comic reliefs) father to have but somewhat fun and inspirational too. I expect more to come from him when battling Aizen now.
I do not know about the rest of you guys - but when this 3 comes out - whether on the Manga or in the Anime - with their irritating behaviour I somehow find it INSPIRATIONAL. What about your favorite Bad Ass Characters (be it your heroes or villains).
Others may states Gin Ichimaru (chopping Jindanbao's hand - and that smelly smiles) and Aizen Sosuke (the whole thing - 'Bad Things' about Bleach), Barragan Luisenbarn, Grimmjow, Ulquiorra, Nnoitra, Szayell even Captain Mayuri Kurotsuchi and Byakuya Kuchiki - but you are all welcome here to state your disagreements (and so to all that in agreements).
Sometimes Bad Ass Guy can be your Heroes too. Thus for me it is Hollow Ichigo, Kenpachi Zaraki and Isshin Kurosaki (eventhough he is a comic reliefs).