What monumentally stupid thing did you do as a child that you're now surprised to have come through unscathed?
Here's my comment:
I'm surprised nobody's mentioned swings yet. I was a swinging dare-devil.
For anyone who ever saw the old Nickelodeon short cartoon "Inside-out Boy," I was convinced that if I got enough momentum, I could go right over the bar (although I was fairly certain I wouldn't get turned inside-out, that would just be an unexpected bonus).
While such attempts were unsuccessful, they led to an even more exciting habit: jumping contests for both distance and height. My mom got mad every time I came home with another shirt that got torn on the chain of the swings, I was mad that it ruined my release, thus costing me precious inches on my jump.
I also developed some entertaining swing tricks: The Tarzan, in which I'd jump off the seat, grab one of the chains, and swing back and forth until the momentum ran out. And another favorite which I never managed to name (but still scares friends when I do it now), but I'd straighten out at the peak of the backswing and keep stiff through the arc, so I looked straight at the ground (and my head came just inches from smacking into the ground) then the chain would slack, because my weight wouldn't shift, and snap me back up. This went seamlessly into the backflip, when I'd let my legs fall back and effortlessly (once I got the timing right) dismount the swing flat on my feet.
What crazy things did you do as a kid?