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.
There might be trademark law involved with this. One of the creators like George Romero or someone might hold a trademark on the word “Zombie” for use in films.