Haven't ever really been scared by movies. Just the parts that startle you, like where something jumps or makes a loud noise.
Invited a girl over to watch the grudge once, and we paused it so she could go to the bathroom. I turned out all the lights and hid behind a pillar. When she came out of the bathroom and past the pillar I made the grudge noise and made her cry. It was pretty fun. Dated her for another month or so.