I would have to say:
The Ring, esp. with that part with the girls body in the closet....eww, I screamed
Urban Legend....I was so scared after this movie I RAN out of the theater and tripped down the steps....oops
Candyman
Red Dragon, the part when Edward Norton is walking in to the first family's master bedroom and you just see blood everywhere....I dropped my soda b/c I was so frightened.
Lots of movies scare me, I Still Know What You Did Last Summer scared me so much that I threw away our copy of the movie, b/c just looking at it scared me