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.
Magic computers that can sharpen and enlarge a grainy CCTV frame enough that you can read what people are typing on their phone.
The American president that goes "gee-haw we really need to stop Voldemort so the people of Agrabad can enjoy democracy and human rights!"
The divorced single-parent cop who struggles to make family life work despite being good at solving big scary crime.
The "we just want to do senseless evil for no apparent reason" terrorists