When I was 12 it came on one of the 3 local networks, ABC, CBS and PBS... Anyway, I watched it in horror. I had never seen a scary movie before so this probably wasn't the one to start with. The Dark Shadows commercials were the extent of it. It scared me so much that I have never been scared from a movie since. Ruined me for horror movies but I still like them and sometimes I can get a little chill or something.
On Netflix a few years ago, The Haunting of Hill House was pretty spooky. There was an episode of the X-Files that was unsettling.
The most unsettling movie I have ever seen by a mile is Room... not to be confused with The Room which I think was a comedy. Anyway, I am not sure what emotion I was feeling... fear was certainly part of it but it is not a horror film in the least, although to me it was horrifying. My wife and I were both shaken. I'm stunned that it didn't affect more people this way. It's not mentioned on any lists, so I guess it will just fade into oblivion.