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.
Once the silencer is on nobody can hear the gunshot or the supersonic bullet or impact on a wall or the bloody wound. That John Wick scene was particularly bad.