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.
Oxygen tanks are not bombs.
I think the worst example of this was a Robert Redford move I saw once where an oxygen tank was loaded in a tube, the stem was knocked off, and the tank flew into a guard tower and exploded like it was an RPG.