I did a variation on the bamboo blackpowder cannon, and it was the plastic pipe blackpowder pistol. It didn't end well, my friend had blackpowder speckles all over his face and eyes, and I had not much skin left on my lower right arm.

There was also the hot summer, midday trek when we got lost in the hills. Well, we found out the way back at last, but it could have been serious :)

I'm not mentioning the bad habit to illegally ( 12 y. o. aren't supposed to) drive regularly motorcycles without helmets. Fortunately nobody ever got seriously hurt.