I was asked once by a co-worker out of the blue if I was a christian, my answer was that I was a "post-modern existentialist". It pissed her off, because I wouldn't explain it and she had to look it up. Which of course made me happy
Mostly my answer to those types of queries is that I am "non-religious". I define that further by saying that religion plays absolutely no part of my daily existence. I'm neither pro-religion of any sort, nor anti-religious. I just don't care.