I tend to say 'gods damn it' and 'thank gods' - hugely pretentious, annoys the fundies no end and covers all permutations. Not that I believe in any of 'em for a moment, but as has already been said, it's a cultural thing, sometimes it's hard to break the habit. And I only use sex-related expletives when truly riled, as I find they're so overused these days they've lost most of their original force.
I do confess to a sneaking admiration for the expletive used in Ghostbusters, though - 'mother pus-bucket!' Sounds most unpleasant... (the pus-bucket part, I mean. I'm a mum myself, we take enough flak as it is.)