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.
When the driver of a car is looking more at the passenger they’re talking to than the road. Probably a dead giveaway that the scene is shot with green screen or the car being towed on the back of a truck.