I'm not scared easily. I rolled my eyes at Saw movies and Hostel made me want to travel to Europe again. A good horror movie (to me) messes with my mind, might have gore, and has a couple jump out of your seat/hide behind your pillow moments.
Mothman Prophecies combined two of my biggest fears - collapsing bridges and drowning. "Wake up, number 37" still gives me chills. Also, there is no pat resolution in the end.
Jennifer Carpenter knows how to do good scary movies (The Exorcism of Emily Rose is in my top 20 which also has Laura Linney). This movie has it all - claustrophobia, gore, creeping dread, and a lot of good jump out of your seat moments.
I'm a sucker for any angel/demon stuff. I think this movie has a whole new level of creepy/scariness since it involves a pregnancy and horrible things done to a woman.
I saw this movie when I was 5 by accident at our vacation home since it had HBO. So, I'm sure the movie is lame as an adult but that tequila bottle scene? Any movie that does scary shit to kids, ranks pretty high in my personal nightmares.
Don't ask me how young I was when I saw this movie. I still to this day get freaked out by masses of birds at a playground. Scarred for life.