Off the top of my head...

original Nightmare on Elm Street - Tina's death
Saw - the reveal
The Ring - girl coming out the tv
Poltergeist - clown doll isn't where it was a second before

I'll think of something soon, but my first ever holy shit moment was the first time I saw Alien as a kid with my mom, the vent scene :)

Also the corpse in the hull of the sunken boat in Jaws.


Saw both of these films when I was 6 or 7 and jumped so high at both of those scenes.

Ti West's House of the Devil, the "Are you not the babysitter?" scene.

I've seen Alien countless times, and this still scares the shit out of me.

Also, the end of Sleepaway Camp, for sure.

That's a great one :)Also the last 15mins of Audition

Evil Dead 2 - at the end when the giant tree boss shows up and pretty much everything happening from there is one big "holy shit" moment.

Cabin in the woods - The ending when everything goes crazy.

I shouldn't say they are my "favorites" but some freaking holy shit moments indeed...:D

The Oldboy twist
A Serbian Film ending
Most of the parts of NEKRomantik
Inside's "Cesarean" baby birth scene

Got to add when the tree with sexual intentions goes at it in the original Evil Dead. Comic genius.

The reveal of "the skin i live in"

Some memorable holy shit moments for me is

@Roshiq - I agree with the "Inside" scene. I can't really show any friends "Inside" after showing them "Martyrs". (they'll still watch all the other foreign films i have though) lol

The ending scenes to "Wait Until Dark" - great scare in one of my favorite movies

When the radio first clicks on in "1408" - sitting in silence and when you least expected it blasts through the speakers, a subtle scare, but it works

That's what I can think of off the top of my head. I know theirs more shocking moments out there though. :)