I was mostly on the supply side of the "creepies". Most of the time, it was things like startling people during a spooky, suspenseful part of a movie. Halloween was the best time for scaring kids before all the PC nonsense got started.
Once, I was dressed up in a black robe and hood (with a dark mask to hide my face in the dark). I stood motionless in the yard with a severed head in one hand and a scythe in the other. Most of the kids seemed to stay well away from me, but there were a couple of wiseguys who wanted a closer look. They actually seemed convinced that I was some kind of dummy. One of them kicked my shin, but not hard, and the other got right in my face. He wasn't more than a foot away, but because of the mask, he actually thought I had no face. As they went on their merry way, I started walking after them, but it wasn't until I threw the scythe at them (really a homemade boomerang that returned for an easy catch) that they really freaked out and took off running.
Another time, I dressed up like Freddy (complete with the red and green sweater and a load of makeup) while by sister answered the door. When everything was all set, she answered the door, and I would jump out from behind and seemingly stab her in the stomach. She'd released the fake blood and fall down. Then I'd turn to the kids at the door, and they would take off running as fast as they could.
We didn't get any trick or treaters for the next few years after that.