Insects (pretty much anything with more than 4 legs is a problem for me, although I don't mind shrimp in my tanks). The more legs, the creepier it is.
And kids - for some reason kids - especially teenagers - freak me out. I wasn't one all that long ago (less than 10 years to be precise) but even then they made me nervous. I've always been much more comfortable around adults. I have no idea why. It's just the way I am I guess. May also be why I never had kids of my own. At least not yet.
I'm scared of trolls. Silly I know but I can't stand to be in the same room with 'em. When I was 4 we had just read the story about Billy Goat Gruff. The bridge on the way to school was being renovated and I remember a worker had to carry me over the bridge which only had a plank across it. I knew for sure the trolls were under the bridge waiting for me.
Another fear is clowns. My Mom pointed 1 out to me who was driving a Volkswagon. I screamed for hrs. lol