'Pipes' from Ghostwatch. I was 11. First proper Halloween. I'd watched scary films before, like Silence of the Lambs and Poltergeist both of which scared the crap out of me but Pipes was on a completely different existential plane.
I had a lot going on with my parents, too much for a child to deal with tbh. That Halloween was my first proper going out trick or treating, the first and only one which actually felt like a halloween. Then I got home and got to watch a Halloween special with Craig Charles from Red Dwarf no less. I believed it was real and I freaked out, so instead of letting me watch the end they sent me to bed and I just kept waking up screaming. I remember them being so angry at me because I couldn't settle.
For probably a year afterwards I used to lie terrified and alone for hours in the dark listening out for any noise and trying to be as quiet and as still as possible. I didn't really get over it until I was about 13. When I rewatched it as an adult I realised it would have been so much better if they had just let me watch the end.