I'd say swinging on a rope tied to a tree above a dried creek in the trails. My grip wasn't strong enough, and I fell down like 12 feet. Luckily there was a slope beneath me so it wasn't a straight drop, but I fell like 8 of the 12 feet, however there were rocks and shit, and it hurt bad. I was like 8 then.
I don't know if this is my scariest moment, but it's the best one I can think of at the moment.