Depending on your age and what you're exposed to, there has to be a movie that absolutely scares the piss out of you. Mine would have to be Pet Cemetery. I saw it when I was young and it's stuck with me ever since.
idk, the freakiest upcomming tho has to be Quarantine. They trailor was screwed up looking. It has the same camera work as Cloverfield(the home video look). heres a site about it [url=http://www.imdb.com/title/tt1082868/]
I always (or almost) liked horror films, so i wasnt shocked as far i can remember; but i can say i felt something XD with Eraser Head and some war scene.
Hmmm, I think it was Saw 1 - 4. It's so disgusting and all! I nearly piss my pants and scream to death! Sigh, good thing they don't make a 3d out of it!
They did, Saw 3D, but I'm unsure of the actual title.
As for me, the Jurassic Park series did have me going, but I was mostly startled. ONE SCENE of Alien did have me going (I was forced to watch.), but, I'd say the trailers for the A Nightmare On Elm Street did it for me. It was bad enough that I occasionally play the game (I am a little paranoid).