Bugs? Spiders? Snakes? Flying? Losing? Certain colors? Heights? Crowds? Your pants falling down in public? Death? Fear itself? What are you afraid of and why?
I think my biggest fear is pain. This includes mental pain in it. It's really scary when all sorts of emotions just rip you apart untill you don't know what to do anymore and you just want to scream:P Very scary. This also includes being left alone by people etc, because that's very painful:P