Clowns and spiders scared me as a kid, and still do.
When I was younger, I had the most irrational fears when I went to bed. One was the fear of cutting off my circulation in my wrists by sleeping with my forearm under my pillow, which my head was pressing down on. The other was the completely irrational fear of having a needle stabbed into my bellybutton.
Yeah, WTF, I know, right?
Silverclaw, I would ALWAYS see scary things in blanket folds too! My senses get all enhanced and I start forming images and hearing sounds that aren't occurring. I once got mad at a kid in my health class in middle school when we were discussing our fears. I never liked the dark (and still don't), and he commented, "Well how can you be afraid of stuff you can't see? You can't see anything in a shadow!" and I'm like, "OhhOHHHH, but you CAN, good sir!"
I also never watch horror movies. So in the odd event that anyone on this forum dates me, never take me to a horror movie.

Edit: I also remembered watching E.T. when I was younger, and for some reason, I got the most terrible fright from the scene from where Eliot is visiting E.T. in that makeshift alien hospital thing, and E.T. is all pale and sickly and dying... I almost peed my pants, I think, because I was just so disturbed by that.