Twilight Zone used to scare the crap outta me when I was a kid.
I saw a handful of horror movies when I was young that freaked me out. Tourist Trap, The Incredible Melting Man and the original Halloween and Amityville Horror. Michael Myer's look was the stuff of nightmares and the scene where that window closed on the boy's fingers in Amityville freaked me.
That G.I. Joe episode in which Dr. Mindbender created a machine that turned humans into animals. The scene where Cobra captured Iceberg and turned him into a Killer Whale in Mindbender's machine was too disturbing to me, I never watched that episode again. Holy s--t!