Weirdest thing I've sold: An Autotaser:
"If the AUTO TASER’s ultra sensitive vibration detectors sense an intruder, a screeching 120 to 130 decibel alarm is sounded as a warning before aggressive countermeasures are initiated. Five seconds later, a field of electrons completely surrounds the unit. Any attempt to touch the AUTO TASER zaps the thief with an unforgettable, yet non-lethal 5,900 milliwatt (50,000 volt) electron pulse."
Bought it in Edmonton, and sold it after apprehension the sucker would go off at any time. Had a bidding war breakout for it and sold it to some German dude on vacation in the US for a 100% profit.