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.
Grenades. A hand grenade has a kill radius of 5 meters and an injury radius of 15 meters. You’re not going to toss one around a corner and survive.