Fireworks!
When I was a teenager, most of my peers were interested in smoking cigarettes and drinking alcohol. Neither of those activities appealed to me, but I was fascinated by fireworks.
I was living in Germany, and there, fireworks are legal to sell only twice a year -- for a couple of weeks before New Years, and during Fasching. Fasching is sort of negative Lent. Since people are going to deprive themselves of pleasure during Lent, they have a period before Lent, Fasching, during which they throw wild parties, which sometimes involve fireworks.
Many stores would sell fireworks. Legally, you had to be 18 to buy them, but most stores would bend the rules and sell them to minors.
My parents, especially my mom, didn't want me to have them. She was afraid I would get hurt.
So if you were a kid, you had to A: save up your money before the season during which fireworks were available, B: buy them, and C: hide them from your parents.
Year after year I did this.
I remember, when I was in 5th grade, I did have one explode in my hand. There were 'screamers', which made a lot of noise but were safe to hold in your hand. But they said on them, "Don't hold in your hand", in German. I bought another firework that looked like a screamer, but it was a different color. It said "Don't hold in your hand", but since screamers were safe to hold in your hand, I ignored this. It screamed for awhile, then got quiet. A little flame came out and I wondered what it would do next. Then "BANG" -- I got my answer. It was very small. The explosion was painful, but did not harm my hand. I never told mom about that, of course.
Once I tried to make a hand grenade. I put a very big firecracker in an empty soft drink can. At the time, German soft drink cans were steel, not aluminum. I took it into the forest near where we lived and threw it in into a gully where the shrapnel wouldn't hurt anybody. It was quite a disappointment -- the explosion just blew off the end of the can, the rest of the can was intact -- no shrapnel was formed.
I remember one type of firework I had, it didn't have a conventional fuse. One end was sulfurous, like a match head, and you struck it on a match box and then it would flame like a blow torch for awhile, then the firework would explode. Once I was in the woods and I lit one of those and threw it down a steep hill in a forest. It landed in a tree, 40 feet up. The first 30 feet of the tree didn't have any branches, so there was no hope of climbing the tree. More and more smoke came from the firework and I realized the blow torch was setting the tree on fire. I was worried it was going to start a forest fire and there was nothing I could do to stop it. Then the explosion came, which blew the fire out.
We generally didn't have forest fires in Germany, the place is too wet.
In Germany, I went to an international school, and our school had an American Boy Scout troop. We would go on camp outs with other American troops, virtually all of whom were military kids. Military kids rarely went off base, I don't think most of them had German money in their pockets. So they didn't know they could get fireworks from the Germans. I went around at a camp out selling fireworks to Americans at a hefty profit.
I remember a prospective customer didn't like it that the fireworks didn't have a conventional fuse. I showed him the troop number on the shoulder of my uniform and promised him that if he couldn't get it to light, he could come to my troop and find me and he'd get his money back.
The next day I was walking along and I saw him coming the other way and he had one eye bandaged. He said "The firework blew a hole in a tent.". I was freaking out, thinking he'd injured himself with the firework I'd sold him, but he realized what I was thinking and told me the injury was because of something else.
What had happened is that the guys in his troop were very skeptical that the firework would work, and someone had been sitting in a tent, slowly striking it against a matchbox, then it went into blowtorch mode, so he threw it to the other side of the tent. While still in blowtorch mode, it burned a hole in the tent.
When I was 15, I got word that my family would be moving to Australia in a month. I met some grownups who had lived in Australia, but I couldn't trust them to ask them what the firework situation was there. They would think I was too young to have them and fink on me to my mom.
I had saved up some money from a job I'd had selling refreshments at movies that were shown at my high school, and I spent basically all of it on fireworks. My dad's company was going to ship everything we had to Australia, even the food in the pantry.
I hid the fireworks in a lot of different places. I took a lamp apart and stashed some there. I put some in the pockets of my mom & dad's military uniforms in the attic. We had some American cake mix in the pantry, so I made a cake, filled the box with fireworks, and glued it back shut.
I hid the fireworks in about 8 different places, and wrote a list of those places. When we moved to Australia, it took about 8 weeks for all the stuff to get there by boat, and during that time, I lost the list.
When the stuff arrived, I collected my fireworks as best I could.
In Australia, soft drink cans were aluminum like in the US, so I repeated the hand grenade experiment. Again, no shrapnel, but the bottom of the can was blown out into a half-spherical shape.
A year or two after we arrived in Australia, my mom opened up a box of powdered sugar to find fireworks inside. I'd forgotten about those. By then I was old enough that she was cool with me having them, so she just gave them to me.
A few years later I was in college in California, and wanted to take my fireworks there. Returning from a visit home to Australia, I smuggled some in my suitcase. I knew they did not pose a danger, because I had been experimenting with fireworks for years and knew that if they went off, they wouldn't even blow the suitcase open.
Years after that, I saw a sign at an airport saying the penalty for carrying explosives on an airplane was 5 years in prison and a $25,000 fine. Sobering.