When the boat turns evil on H.R. Pufnstuf: I couldn't have been more than 3 when I saw this movie, so it's not surprising that when the innocent sailboat Jimmy gets on turns evil, I firmly planted myself behind the couch. I still kind of get creeped out by that boat, it must have been powerful.
I'll admit I never saw the film until I was a teen but the ad campaign for it gave me nightmares. I always found Ventriloquist dummies creepy to being with, so this really didn't help matters much. A close second to Magic would be the ads for Killer Baby movie "It's Alive" (which they are remaking) the site of that creepy hand coming out of a crib was disturbing, I was a sucker for such things.
Sleestaks: If I ever get a chance to meet Sid and Marty Krofft, I won't know whether I should thank them or start swinging. I spent many a Saturday morning behind the couch because of these guys, eventually my fear turned into complete obsession, which is were I've been for the past 32 years.
Almost frigging every minute of Willy Wonka and the Chocolate Factory: My parents probably had good intentions when they sat me in front of this (They also thought Animal Farm would be appropriate because it was animated, whoops!) I didn't jive with any of it, The OompaLoompas? Scary! Jack Albertson? Scary! The Ironic punishments? Terrifying, especially when Violet blows up, I've heard some people developed a fetish after seeing that, I think I prefer to be scared but to each their own....
The very sight of Jon Pertwee : Doctor Who was freaking scary when I was five and I respected/feared star Jon Pertwee and that haunting title theme. I remember my father mocling the show one Saturday night and I turned to my dad and said "No, don't make fun of Doctor Who!" I was actually worried for my father's safety.
The Robot Scene from Superman 3: If Richard Pryor wasn't bad enough, the film had a scene of a woman being turned into the most fantastically creepy robot ever, right in the middle of an effing Superman movie. Your guard is totally down and then BAM the producers shove in some good old fashioned nightmare fuel like a shiv in the back!