Nice question :)
In my opinion, Killer B from Naruto Shippuden.
Because he is the one character out of all anime that always believed in himself. After being treated like trash, despised, betrayed and even sought to be killed by his best friend, he still didn't doubt himself. When his village threw stuff at him as he walked down the streets, he only smiled. He had such a hard life but he still kept his head up.
He is such a funny guy, who doesn't care what others think of him, is very loyal and shows understanding towards everyone because he knows how it feels to suffer. He even managed to tame and become friends with a tailed beast which previously knew nothing but hatred, and he forgave his friend who had almost killed him. That, in my opinion, takes real guts.