Theremin
I built this theremin when I was 17 from plans I found online. It was my first electronics project, and quite an ambitious one at that. I made the circuit board by ironing on a mask and etching away the exposed copper. The two coils were hand-wound around PVC pipe. I used a kitchen whisk as the antenna.
The sound is more distorted now than when I first built it, but it still works.
