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 feel like there’s a lot of script writers that want the emotional wrenchingness of “this character’s personality and history means that they will never see the simple solution” but have no idea how to actually pull it off.
Breaking Bad pulls this off wonderfully multiple times, where the “right” decision is right there but for the character to be able to do it, they couldn’t be who we’ve learned them to be so far.
But most directors amd scriptwriters are nowhere near that level.