Riding my motorcycle a vehicle was stopped in the middle of the highway with no hazard lights on. The roads were cold and my front tire slipped while trying to swerve real fast and I missed the truck by a foot, while my bike slammed into the back. I probably slid down the road for 100ft. Always where your safety gear, as I got away with only road rash on my knee. (wasn't wearing riding pants)
Another time I was wrestling a friend who we were trying to throw in the lake. He was #1 in state competition (we had like 5 guys on him) but he threw me to the ground with my head about 3 inches away from a big enough rock to kill me had I hit it.
My dad had this bright idea to put the jumper cables in the engine compartment of a 1991 Pontiac Caravan. The jumpers made a connection with the accelerator input, and it shorted it so the car was just as if you had the pedal floored. My mother didn't know what to do, so she held the brakes as hard as she could and we went off this off ramp into a burger king parking lot and threw it into park 
we were lucky no one was coming down the road cause we sure weren't stopping for them.
I probably was in no more danger than breaking a leg or something, but I thought I was going to die while I was in the air. This one time my brother told me if I don't hit this quarter pipe that had worn down (we would jump off the front and land on the back) that he was taking the stunt skis I was using. So I hit it, but way to fast, and was probably 30ft above flat ground at my highest. When I hit the ground, I left a dent in the snow about 3 inches deep, my ski's immediately popped off and I slid down the hill for probably another 30-50ft through mud and wet snow 
EDIT: so I've never been seriously injured, but I've came awfully darn close
