In middle and high school I loved to build weapons from legos. Most of these creations can be found on my legogunguy001 channel on youtube.
During middle and high school I had a big passion for creating fireworks from raw chemicals. My proudest creation was a 3-inch ball shell for some other kid's birthday party.
Hydrogen (HHO) torch
This device I built for a science fair project where using electrolysis create enough hydroxy gas to power a torch. I built a power supply which would supply around 40 amps at 12 volts to an electrolytic cell that I also built.