What's your deepest, darkest fear? Have you tried to overcome it?
While it's true, as jaded_jamie says, that spiders are of the devil, I'd say my biggest fear has always been of failure. I'm not exactly the king of self-confidence, and it took me many years just to accept that I was a good writer -- let alone that I might be able to sell my fiction someday. Now that I've sold my first book, I suppose I'll transfer my worries to selling the next one!