Pic related. When I was a kid I was walking with my mom along the road just down the street by a treeline and tied to one of the trees by it's neck was a baby doll.
Very unnerving.
We never found who did it or why.
Years later I was out with my mom again in another part of the woods and she swore she saw something that looked humanoid and albino, like all white. It scared her enough that she wanted to leave right then.
Still think about both of these from time to time.
I hope I have some good ones.
On a run once I found a bunch of wooden sculptures of animals covering half a mile of trail. It wasn't too far out of town but it was kind of a foggy fall day so it was spooky.
On another run I came upon an electric corridor. There was a camper in it with smashed in windows and blood stains around the windows.
I met a hermit once when I was hunting as a kid. We were in an unincorporated area with about sixty residents so it was genuinely the middle of nowhere. I got lost in the woods and so I just went straight in one direction until I hit a road. Ran into the hermit on the road and he told me not to shoot his cats. He had no cats.
The scariest was one night I was going camping on a trail I had been on dozens of times. I found a good spot to go off trail and set up and a little ways in I found a plywood shack just filled with garbage that had writing all over the walls.