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.
I have grown to really fucking hate deus ex machina in any form. Luck is always a factor, but c’mon. It usually comes down to lazy writing and they just couldn’t be assed to come up with an explanation.