Audiences are expected to be massive for 'Paranormal Activity 3' this weekend, and if the film does its job, they'll potentially need to rush home soon afterward to change underwear. That's because fans of ghost stories have one easy-to-follow request: "give us a good scare!" While viewers wait for 'Paranormal Activity 3' to deliver on that promise, you can rattle your nerves right now with a look at some of the most memorable paranormal scenes in movie history. Warning: not for the faint of heart!