The first half of It scared the bejeebus out of me, although the ending was a big letdown, I felt. Relic was another one that was scary up front but petered out at the end. The Thing, however, scared me pretty much all the way through.
When I was a kid there was some messed up stuff on PBS, including a vampire series that was downright freaky. All I can remember now is they made this girl wear a garlic necklace. Another one had snakes that used mind control on people.
But the movie that impacted me most as a kid (and would probably seem stupid now), was a British (?) film about these alien things that looked sort of like tortoises with long snake necks that attacked people and animals, leaving a white carcass that looked suspiciously like foam rubber. Nothing f***s up a kid like a foam rubber poodle carcass! Sometimes I call my mom and cuss her out for letting me watch that. Does anyone have any idea what the name of it was?