Christian, though I don't like the idea of saddling kids with explicitly religious names. I just don't like the sound of Cary, despite the lovely CaryGrant as a namesake, and Cain is one of those Biblical bad guy characters that you can't really argue a more positive interpretation for.
It sounds weird, but for some reason, I never found Christian super religious. I mean, obviously it is, but I just never made the connection somehow, despite how obvious it is. I'm very sure of my atheism, but love Christian.