What are some REALLY SCARY movies?

Me and my friends are planning to go to their house and watch scary movies right before Halloween. We soo crazy ! HAHA . But the thing is we can't think of anything scary. Can you recommend a REALLY scary movie for us to watch? I don't want a gory, bloody movie the Saw series . We're looking for stuff that will like keep us awake at night and like be scared to go to the bathroom . HEEHEE . It'd be really appreciated ! ;D