I’ll go first. Mine is the instant knockout drug. Like Dexter’s intramuscular injection that causes someone to immediately lose consciousness. Or in the movie Split where there’s the aerosol spray in your face that makes you instantly unconscious. Or pretty much any time someone uses chloroform.
In the opening sequence of Final Fantasy XII, two separate characters get stabbed through the “stylish” gaps in their armor… and somehow this doesn’t prompt anyone else to reconsider their armor choices.