My story pales in comparison to many of the posts here, but on the other hand I'm thankful I haven't had too many scary or creepy things happen to me.
Near my old house is the abandoned parking lot of a golf course that was closed in the early 90s. It's a secluded parking lot and of course that is a magnet for teenagers getting into all sorts of mischief.
One night in my early 20s, some friends and I were reminiscing about the place and decided to hop in my car and go for a late night visit, maybe scare some kids who were making out in their parents car or something like that. We got there and aside from the lot being in even worse shape than it had been in my own teens, it wasn't much different. There was also trash laying everywhere, so perhaps people were now using it as a dumping ground.
After a few minutes of more laughs about the good old days, we decided to leave. Among all the trash there was a larger than usual pile of it located near the center of the lot, and being young and stupid I thought it would be funny to get a bit of speed and drive my car through the trash pile before we left. I rolled the car into position and just before I moved my foot to the accelerator I was overcome with a really weird feeling and switched on my fog lights instead.
At that moment, a very disheveled looking man raised his head out of the trash pile and looked at us. From the look of him he was probably sleeping off a large quantity of booze, but aside from looking like a hobo there wasn't anything out of the ordinary about him. Still, his appearance was so abrupt and unexpected that we all started screaming and I turned around and drove out of there as fast as I could.
It wasn't until about a mile down the road that I realized how close I had come to running over and likely killing someone. Still haunts me to this day how I got that weird feeling and what would have happened if I hadn't heeded it.
tl;dr: Almost ran over a bum who was sleeping, concealed in a pile of trash.