[quote=UnseenShade]
Atheist doesn't mean denying existence of uber powers, but the character wouldn't see them as gods, just very powerful beings. Insofar as my knowledge of Chaos Gods, that is not a problem for the most part as long as they are recognized.
[/quote]

Hanging out with a bunch of chaos worshippers and not worshipping chaos is kind of an issue though. You will not benefit nearly as much from a lot of things and I cannot exactly give you atheist powers. That is disregarding the simple fact that anytime something bad happens there is a decent chance they just sacrifice you as the most worthy sacrifice to the gods and lack a patron to protect you.