Cristian Martínez’s Kraft Test Drummie and Robert Plant electronic musical instruments are super cool, and were even winners of the Made of Imagination contest in the category of Homemade Instrument. From the contest site:
Cristian Martínez’s submission is a modified toy affixed with metal sponges, car antennas, and crocodiles clips. He is accompanied by his friend Isis Abigail on an oscillator, using herself and a plant as variable resistor. I love how Isis’ really goes off near the end.