WHAT'S THE SCARIEST MOVIE IN THE WORLD?!

So who is it?  Who's mask makes your blood run cold?  Who's theme music forces tingles down your spine?  Who's bloodcurdling voice keeps you up at night?  

Although there are so many different types of horror, I think everyone's beliefs influence what really scares them.  I personally find that my weakness lies in any situation that can happen in real life.  Everyone's interpretation of realistic horror differs, but I think we all can agree that a "Saw" killer or even a Kevin Spacey character from Se7en can physically kidnap and kill you at any second in any place.  But how does everyone feel about The Forth Kind or any of 484,739 movies about exorcisms?  Just because it doesn't scare me on my television doesn't mean I am certain of its incapability of really happening.  

So I am curious...I want to know what scares YOU!