Well perhaps this movie isn't scary to most, but Paranormal Activity was pretty bad for me. I had a couple childhood experiences shortly after my mother passed away that were pretty abnormal. Since that point, I have never been one to watch paranormal-focused horror movies. But my wife talked me into shortly after the movie came out and man, that was such a bad idea. I slept like crap for nearly 2 weeks.
I can watch slasher flicks, gory horror, and pretty much anything else that isn't paranormal-related all day long, but there is just something about those paranormal movies (especially paranormal activity) that just rubs me the wrong way.