I make small flares/bombs with my friends using empty soda cans that we fill with ingredients, then use portions of the metal and string to create the detonator/fuse.
We had a large stock since it had been a while since our last war, so we decided to gather 5 cans, tie them together, attach all the strings to one detonator, and...
...put them inside someone's locker.
Being the richard(s) that we were, we picked at random. It ended up exploding the forget out of the inside of a nice girl's locker as soon as she opened it.
And because I'm a richard I still laugh when I remember that. Never got caught for anything.