The star on the HP-15C's display screen

[Dave Shaffer]

Try loading your water pistol with salt water and then squirting into a 120 VAC socket! Makes a wonderful arc until the circuit breaker blows. Tried only in the bathroom of the men's dorm when I was in college (many(!) years ago).

Or, 6 V grain-of-rice bulbs glow real brightly - for a few seconds! - at 25-50 volts. This has been experimentally verified (as any good scientist, or batch of summer students, would do).

I'm guessing most of us here tried stuff like this at some time or another.