Not even scary, but I watched "It" as a very young child and I was mortified of not only clowns but bathrooms and sewers for many many years to come. Every time I'd flush I'd run out as if my ass was on fire
Paranormal activity 1. When I watched it, I have no clue what it is. I was home alone. In my living room. Night. No light. Just TV. When the movie has finished, after some time my TV has turned off. I was still too scared. All of sudden, I saw some shadow moving in our hall. I was like, wtf? It must have been some ghost! But later I realised I have lamp behind me. So I turned the light on. And later on I realised that there were subtitles on the end, so it wasn't real! 😂. But I almost sh*t in my pants before I noticed it wasn't real.
The 1960ies uncut first version of The Texas Chain Saw Massacre. It was underground. It only made the theaters after much cutting, isn't even listed on IMDB. Not sh~~ting pants but as disgusting as a Spanish small town corrida.
A movie with stop-action puppet animation I saw in school when I was seven. The wolf came to the village - actually it was the carved head of the wolf with howling - and the hunter or whatever he was killed it to save the villagers. I had nightmares about it for years.
The Japanese Ring. Watching it half asleep with no sound and in black and white from what I could remember. Imagine waking up and seeing the woman crawling through the T. V. After this film I'm scared of mirrors for about a month. Why, cause there's a scene where she is with the mirror. Imagine if you see that thing in the mirror and it's behind. There's my point.