Pennywise the Clown, scarred my childhood.
Of course, nobody... likes clowns. Nobody.
So much this. I was at my Babysitters when I was 7 waiting to go to the Zoo with them, and for some reason they had "IT" playing and I got to watch the whole thing. It's hilarious to watch now, and while it wasn't really that scary then; I never stopped thinking about it. All sewers made me think of IT, refrigerators, school showers and even rusty sinks.
Jurassic Park I was also another one of mine which I saw when I was even younger; it was cool and traumatizing at the same time.
I also saw the original AmityVille Horror when I was young and that made me scared of any dark or weird looking houses I ever saw; not like afraid of them literally but idunno.. even now some houses give me chills when I see them.