I’ll go first. Mine is the instant knockout drug. Like Dexter’s intramuscular injection that causes someone to immediately be unconscious. Or in the movie Split where there’s the aerosol spray in your face that makes you instantly be unconscious. Or pretty much any time someone uses chloroform.
Zombies in the George Romero tradition are basically just animated through magic. Otherwise it would be a World War Z (book) situation where the zombies would eventually just decompose entirely.