when I was in the 5th grade, I got to go down to Corpus Christi, TX to visit the USS Lexington with my Webelos cub scout patrol on the chance to be able to stay the night on the ship. Well, night before we actually got there, stayed in a motel nearby and dad just had to watch the movie Ghost Ship on the room's TV and I of course watched also. Let's just say...I barely got any kind of sleep on that aircraft carrier because of the images running through my mind of how the characters in that movie died, and me being stuck in the pitch black crew's sleeping deck on a real life ghost ship. This was also after the staff of the ship held a ghost story event in one of the anchor rooms, some hiding in nearby rooms banging on walls and turning stuff at key points in some of the stories.
All in all, I loved being able to explore the ship, it was absolutely incredible seeing much of the structure, but I'll be damned before I stay another night on that thing because of my highly-active mind

When I was a kid The Fly freaked me the FUCK out. More recently, I thought Antichrist was a really damn good movie.

There was also this one movie which I can't remember the name of, but there was this one scene where these people were trapped inside of a house, it was very grey outside and then like a gigantic flock of birds just start to circle the house and violently cover it in bird shit. As a kid that scene always scared the hell out of me for some reason. Was it even a movie??

i can't tell you what movie scared me the most, but i can tell you what game.
when i was but a wee lad, we got a new computer, and the guy we got it from had preloaded a crap ton of freeware games on to it. one of the first ones i played was wolfenstine 3D, and boy did i freak out from the blood and gore of killing my first pixel man.

Not a horror movie but as an 8 year old Gummo fucked me up so so bad, still does so much i cant watch it,

Coraline...

Probably the one I still have nightmares about is hostel 2. Since all that shit COULD technically happen :(

Oh man, I totally feel you on Twister. I was forced to watch it as a kid and I never really recovered from it, haha. Natural disasters and possible-apocalyptic crap scare the hell out of me now.
Other movies that really messed me up was Final Destination (another movie I was forced into watching. Honestly, who the hell takes a little kid to a movie theater to see that?!), The Happening, pretty much anything that is realistic horror or possible apocalypses means I'm peeing myself scared, haha.

i actually was terrified after seeing the truman show as a kid.. like what if i didnt know people were watching me?? i still get paranoid sometimes because of it but ive never watched it a second time

When I was a kid I was around while my parents were watching Flatliners and that movie scared the piss out of me. I bet it wouldn't be scary now but I was so upset by it back then that I never want to even give it another try.

As a teenager the end of Braveheart really disturbed me... I didn't expect them to actually show graphical torture on screen. :S I think I ended up hiding behind my partner and asking him to tell me when it was over.

the first movie that really scared me was signs. it hit me when i was super impressionable about life in the galaxy and i never once considered that they would want to cause harm. so yeah, that really messed me up lmao. and then a few years ago the fourth kind came out..i saw it in the movie theater and i was so scared by the end i had to call my mom to make sure she was okay.. !

Paranormal Activity....the first time I saw it I was on shrooms so I thought it was real. Never really got over it
Also saw the bababdook about a month ago and that has stuck with me as being pretty scary!

This is a good question aha

As a kid I loved the movie Ghostbusters but the demon dog-things gave me nightmares for absolutely years. I mean look at them, how do you NOT have nightmares about this http://www.top10films.co.uk/img/ghostbusters_dogs_dana-possessed.jpg

As an adult I find it difficult to get scared per se, more like I get disturbed by some moments in movies? The only one that has ever given me the heebies is the Pale Man scene from Pan's Labyrinth, I was gripping the chair arms in silent terror watching that from the moment he popped his little eye-ballers in.

I love questions like this!! I'm a huge horror fan and actually have been working on a series of dissertations on what makes movies enduringly scary and why it's sometimes not even a horror movie.
Drama can leave more lasting impressions of terror than a lot of movies with the intention to scare the audience, and I find that really compelling.
So I hope you don't mind if I comb this thread haha.

To answer your question though, I think the movie that scared me the most was probably The Sixth Sense?? Eraserhead also affected me pretty deeply and I had to watch it in segments because I was so tense.

Signs fucked me up as a kid
it fuckin freaked me out so much i couldnt even finish watching it i cried and had nightmares its was terrible lmfao

Jurassic Park, for a movie that really affected me. My mom let me watch it when I was like 4, and it gave me nightmares for weeks, then when we went to Animal Kingdom in Florida and went on the dinosaur rides, I was terrified, jammed my eyes shut the whole time. Dinosaurs still freak me out, especially animatronic ones @@;

Woman in Black really freaked me out the most for more recent movies, I can't think of a horror movie that creeped me out more than that one. Some really unnerving visuals in that movie. Also in the new Avengers movie when The Vision was brought to life, I felt legit scared. XD since I have no idea about the characters or the comics etc., he really freaked me out too in the beginning.

I think when I was about 12 I watched Night of the Living Dead and it really scared and fascinated me, it was unlike anything I'd ever seen before. Jaws and Jurassic Park also scared the bejeezus out of me when I was much younger.

As an adult I'm a little more hard-pressed to think of a film that really wigs me out. Probably the film Pontypool because things are much scarier when they're suggested instead of explicitly shown (and most of the scary events in the film are only heard through radio broadcasts).

Torture movies. Any of them. Slasher gore, horror thrillers, paranormal horror, all of those are things I like and can handle pretty well. But the second a death is drawn out for pleasure I freak out a lot. Martyrs is a legitimately terrifying film for that reason. The Hostel movies, and the Saw movies. The kicker is that I've seen all of them because it used to not bother me, but at some point that changed and now I can't even watch a drawn-out death in a slasher movie.

That being said, we just watched You're Next last night in a pillow fort and it was an amazingly good slasher movie. I loved it!

I was pretty spooked by the original House on Haunted Hill when I was but a young 'un! Now it's one of my favorite cheesy old horror movies.

When I was a kid, my dad was given Stephen King's "Langoliers" on VHS, and after watching that, I was terrified that one would jump out of my closet or something. The monsters were huge ball-shaped creatures with a mouth that split open three ways and had multiple rows of teeth that rotated like a chainsaw. Plus it had Balki from "Perfect Strangers" acting like a deranged nutcase which creeped me out from ever wanting to watch that tv show again.

I like time travel movies. The concept of there being a past, present and future, and that people flew through a time rip into the past and that the Langoliers job was to eat the entire Earth once it became the past to wipe the slate clean was interesting to me. But those lil fuzzballs with teeth gave me nightmares as a kid. :P

Not a movie per say, but a commentary free play-through for the playable trailer for Silent Hills. THIS. PLAY-THROUGH. BROKE. ME.
No joke. I've gotten scared and screamed at movies before, but this. It was on a whole other level. I was a blubbering mess by the end.
I know i'm being pretty hyperbolic, but I have never been so terrified for my life. Here's a link if anyone wants to watch it.
https://www.youtube.com/watch?v=blD2TiavFJA