I was watching one of my favorite comedians Ricky Gervais on his hilarious show "Extras" the other day. There was a scene in which his character discusses with another the nonexistence of heaven and has to deal with some social ramifications of that understanding. Something seemed odd about that and it took me a while to make the realization that I couldn't think of a single other instance of a character in a TV series (not actor, mind you) unambiguously coming out as an atheist.
There was an episode of "Star Trek" where Picard describes how humanity improved when it moved past primitive concepts such as religion, so that almost counts, and a friend of mine says a character in "House" (which I've not seen) referred to himself as an atheist. I seriously can't think of any other examples. Can you think of any?