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.
My pet peve is people who insist I know how to disassemble an M14 blindfolded before my opinion about shooting children is valid.
(I know how to unload most guns, which is the only useful thing to do with them)