Definitely the hallway scene from The Exorcist 3, I've yet to see the full film but made the mistake of watching that clip (after it was mentioned on here) on Youtube with headphones on and the volume nearly at full blast
I'd also say the burried alive scene from The Vanishing, not because it's a "make you jump" moment but because the thought of being buried alive is nightmarish.
And this isn't a film moment but this scene from Armchair Thriller shook me up quite badly when I first saw it on the Channel 4 scariest moments countdown from a few years ago:
Although after watching it back, it does look quite silly.