What's a movie that scared you the most?

I've seen quite a lot of movies that are considered disturbing as hell, but the one that scared me, GENUINELY scared me, is Saw.

I just can't imagine waking up in some random place alone, tied to a machine that will kill you off painfully if you don't cut into your own eyeball and retrieve the key. Or your family being threatened unless you kill a person that is with you, while you're trapped in a filthy germ filled bathroom chained up. Or you wake up naked in a maze filled with razor-wire, and in order to escape from the trap before an automatic door locks you in forever, you need to crawl through the maze, slicing yourself into a mush in the process. And all of that happens why? I don't fucking know, you don't even have to be a terrible person, maybe you're just suicidal or something, or the killer didn't think that you valued your life enough.

It's why I love these movies so much.