This song is the theme for a movie called Bad Ass. It's a movie starring Danny Trejo that opens on him beating up some rude skinheads on bus, getting filmed, and becoming the local sensation known as "Bad Ass". It's a surprisingly good movie actually, so I'd recommend you check it out.
This song popped up from time to time though and I enjoyed it enough to tell you all about it. Or at least the movie. Eh, either way, here it is.