I grew up in an area right next to a RR switching yard. We'd often hang out there and just slap various stuff together to see what kind of bang or flame it would make. There were some really good ones, along with a few dud experiments....

Some kids just don't have any sense, though, and go beyond the normal boyhood exuberance in doing the pipe bomb thing - and with black powder it always seems to go wrong when screwing down the metal end-caps. I have a picture somewhere of a high school kid who was doing exactly that in his garage (for a school science project - approved by the teacher!) and blew himself across the hood of dad's car. That was a few years ago - but it was only three months ago that a Mom in Oklahoma was charged with "explosives manufacturing" for buying her teenage son supplies to build pipe bombs.