I'm possibly the worst person to take to a horror movie. My opinion is usually that they're not actually scary, and/or they're just gross. Last night I viewed Paranormal Activity. It had some good scare moments, but for the most part, I was just mildly curious as to what would happen next. I say this having viewed it in a fairly full theater full of people whispering and screaming. This pretty much killed any real fearful mood for me, since I was hyperaware of other people's reactions to a work of fiction. In all honesty, I have to be alone, in absolute silence, with the lights off, and at night for the mood of a scary movie to work on me.
In fact, I usually just watch horror movies to laugh at them. Even better if it's an intentional horror-comedy: it has all the weird horror elements and violence, but I don't have to feel like I'm reacting to it the wrong way. I can laugh and not be scared all I want.
Last night, I kept trying to think of things that really wigged me out. I concluded the worst I've been freaked out by watching something was about 6 months ago, coming home from class and sitting down to watch some PBS. I came in a few minutes into some documentary about some cool religious congregation that turned into a commune that advocated equal rights and loving each other. That congregation eventually moved to Jonestown. Coming in with no context, I didn't know the end of the Peoples Temple until the end of the documentary, and I was chilled. For whatever reason, I had never heard of Jonestown and the events that happened there. I had no idea, and I it was terrifying.
Moral of the story: Give me a real life horror, and I will be so scared, even as my roommates walk in and out of the room and the lights are on. Give me some fictitious story of unexplained phenomenon, and I will most likely just laugh in your face.
And for those interested, you can find Jonestown: The Life and Death of Peoples Temple trailer here and the full thing here. You'll need a hug afterward.