I don't really know of any straight-up badboy Cas fics, but I have a few where he acts like a jerk while Dean is less of a jerk:

If I'm Drowning Please Don't Save Me ('cause I've got to save myself) (http://www.fanfiction.net/s/8573511/1/If-I-m-Drowning-Please-Don-t-Save-Me-cause-I-ve-got-to-save-myself) is a college AU where Cas and Dean act like dicks to each other until they start becoming tentative friends, but Cas keeps being a dick while Dean keeps trying to reach out.

And you've probably already read it, since I think everyone has, but It's Always the End of the World Somewhere (http://scaramouche.dreamwidth.org/222265.html) has a Cas who's fairly devil-may-care (out of a sense of self-preservation) and doesn't treat Dean very nicely at first.