Only film that has made me ruminate on it afterwards was It Follows. I still think about it occasionally now.
Event Horizon scared me when it came out but I was, like, 16.
The Ring - the original Japanese version - frit me a bit when I first saw it, but it's a slow burn. Back in 2000 My fwb housemate and I had got back from the pub on a Friday night and were watching whatever was on Channel 4 while smoking some Js (Graham Norton I'm guessing). That finished and then this Japanese horror film started at like 11pm and we just got sucked into watching it. When it finished at like 1am we were both pretty shook by it. My housemate refused to sleep in her own room (which had a telly) and demanded to sleep in my room (which did not have a telly) which I thought meant I was gonna get some, it being Friday and all, but apparently that film, as well as being scary, was also a complete libido killer. So, yeh, not recommended if you're looking to get your leg over on Halloween.