A person dared me to try out for the school play, so I did. I got the wonderful part of being a horse. The costume designed for me was a flesh-colored leotard, so everyone thought I was....yeah, well my mother and my drama teacher had a nice long chat after that. Yallow
Well, I've never worn any flesh-coloured leotards, for which my peers are grateful I think. But I think the most insane thing I've done with obvious immediate potential consequences was when I was in scouts and we'd fashioned a very unprofessional zipline. They took a moldering rope and some old tire they found, tied the rope to a high tree and a low tree with the tire on it at the top. They were all boasting and daring but I decided to try it out. Once I actually got in the tire and was working up the courage to let go, come-what-may, I was told confidentially (from guys who liked to pick on me and were never friendly) that I didn't need to do this, that they wouldn't say bad of me for backing down. I said it's fine that I want to do it and then I let go. The drop was brief and scary, but only moments later the rope went taut and I was carried partway down the zipline. It wasn't very fast since it wasn't exactly a friction-free setup. The drop was about 1.5 meters and happened because the rope was so slack. After I did it and didn't die, the rest of them went too. Oh, I was about... 10 years old at the time.
Sex in a ... nah, you wouldn't wanna know about that.
I took part in an open mathematics competition in my home town, turned in a single page for the first round (to be done at home), turned in my work after only 45 minutes of the 2-hour exam that was the second and final round, and won first place.
I've done a 2-day leisure walk on a weekend in army gear, complete with camping out under a tree.
Cycling 50 km in the afternoon to see my girlfriend, and cycling back, more than once; one time when I cycled back at night, I fell asleep on the bicycle and crashed into a bush. The nice thing about falling asleep on a bike (as opposed to a car) is that the more you fall asleep, the slower you pedal, so it wasn't actually harmful.