When I was a kid, it was before VCRs and I avoided most scary things on cable, but I loved science fiction and so would watch The Twilight Zone and other shows that were usually twisty, but not what I would think of as scary. But two particular episodes of shows really frightened me:
-An Outer Limits episode in which a house had a pulsing membrane in a room which controlled minds. I always had to turn the lights on in any strange room to make sure that a pulsing membrane wasn't there. Star Trek didn't help with this because they had an episode where jellyfish-like creatures would fly through the air and attack people by landing on their back. Looked just like the membrane in the Outer Limits episode.
-The most frightening experience in my young life was an episode of Night Gallery. I watched it because Rod Serling was so great in Twilight Zone, so I figured this must be more of the same. There was one episode when a man, alone in his apartment, saw a spider in the sink, so he washed it down the drain. Then, taking a shower, he saw another spider, looking just the same but a bit bigger, in the shower. This continued on until he opened his front door and was confronted with a four foot spider. I was scared to go anywhere near a shower from that point on. After my mom finally yelled at me that I needed to take a shower, I would take a bath. No spider would get me then, that's for sure. I didn't take a shower for years.