I'd say Stephen King was my biggest influence because I was reading his work when I was ten years old. Anyone who has written a post-apocalyptic novel needs to give a nod to The Stand. I'd call it the gold standard.
Christopher Moore was a big one, as well. In my eyes he is the godfather of humorous horror. Until I picked up Practical Demonkeeping, I didn't think there would be a market for my style of writing.
I also read a lot of non-fiction from all over the political spectrum. Chomsky and Moore to Nugent and O'Reilly. I don't like to feed my own opinions. I'd rather look at different opinions and see how they shape my own. Being open-minded is becoming a lost art.