I made a simple but really cool switch using foil sheets and a rolling marker. I connected two foil pieces to the two ends of my circuit, keeping them separated so the circuit stays open and the LED is off. Then I covered a small marker with foil and used it as the connector. When I blow the marker so that it rolls between the two foil sheets, it touches both sides, completes the circuit, and allows the 5V to pass through, causing the LED to light up. When the marker rolls away, the light turns off again.
It’s a fun and unusual way to switch an LED on and off just by blowing the marker in and out of the foil sheets.