Cool idea! But I can't narrow it down.
Just of the top of my head, these are scariest scenes:
- The Grudge 2: You find out what was causing the banging noise in the girls apartment...
- Alien: Ripley hums a song while trying get into the spacesuit before the creature wakes up...
- The Haunting: The girls wake up after a night holding hands as something kept trying the door...
But best jump moments, I can't get down from four; "head bob" in Jaws, the attic in The Exorcist, the rooftop scene in Dark Water and the grave at the end of Carrie.
And then, the most disturbing scenes that are just languishing in the macabre!
The zombie feast in Day of the Dead, a vision of hell in Event Horizon, Leatherface whirling his chainsaw around while the girl is probably going insane and the man-in-the-sack having a hearty meal in Audition...