I watched Alien last night. That scene with Tom Skerritt in the air ducts when the alien is in the corner still scares me like it did when I was a kid, and I always expect it too.
Then I watched Descent for the 2nd time. It is pretty good, of course it pissed me off more than scared me. I was like "Shut the *beep* up bitch, it's gonna getcha!!!"