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.
The expert who somehow knows all things science and engineering, like they’re all just basically the same. Just once I’d like to hear, “I’m an astrophysicist, not a cybersecurity expert. I don’t have the first clue where to begin hacking any computer, let alone an alien one that I’ve never seen before.”
Bonus points if the characters have to look for a different solution due to their lack of on-hand expertise in a particular area.
I just saw that in WandaVision. Darcy is an Astrophysicist but was also hacking through various firewalls to get at some secret data.