As promised, here's my entry:
https://youtu.be/fL0nbPd7dcUI'm feeding a 59Hz sine wave at about 12VRMS into the neutral side of a neon-resistor circuit tied to a voltage divider across U.S. mains 120VAC at 60Hz. It's being directly driven by the output of an op-amp with a ground common to mains neutral. By setting a voltage divider on the mains to right around the neon bulb's strike voltage, the 1 Hz frequency component of the summed waves makes the bulb turn on and off.
(Also, this is my first video uploaded that I seriously shot and edited, so yay for that.)