You watched Event Horizon as a child? Damn, that's rough! I watched it as a young adult on TV thinking it was just normal sci fi and was scared shitless by the end...
As a child there was a part of a movie I watched that gave me nightmares for days. It was someone rubbing a bloody chickens paw on a womans leg. That's it, that's all I saw before my parents yelled for me to go to bed but it haunted me for days.
Yeah, I think I was like 8 or 9. I was an adventurous kid, setup the VHS recorder to record it automatically from TV and then watched it when I was home alone.