Falling- I hate the feeling of falling (say on a roller coster), it freaks me out to no end. I hate it when you're driving and you hit a dip in the road, I won't go on rides because of it, I'm a little frightened of flying, etc. It's ridiculous!
I used to be terrified of spiders, but had the chance to hold a tarantula at Longleat Safari Park, and took it. She was a fantastic creature, and although I'm still not brave enough to deal with house spiders by myself, I don't freak out and run away any more.
That's about it really. Aside from being a bit of a daft hypochondriac too