I've got a whole list:
"Because the prophecy said so!"
"Because you're the chosen one!"
There can never be more than 2 female characters in the main group, and if it's an action or horror story, one of them always dies
Men can be killed onscreen with plenty of guts and gore, but apart from a few situations, women either die offscreen or have overly dramatized deaths
Protagonist thinks they're ordinary but suddenly has powers
Protagonist thinks they're ordinary but is the long lost king/queen/prince/princess/grand whatever of someplace they've never heard of
Instant-killing stabs in places that would take forever to bleed out (same goes for instant killing gunshots)
All Asians are either nerds or secretly trained in martial arts
Cars other than the Ford Pinto exploding because of collisions
Modern cars being indestructible when hitting things (modern car bodies are much more flimsy for safety reasons, they'd crumple hitting so much as a signpost)
Someone owning a pristine 50+ year old car that never has issues and works like it's brand new
Low wage job pays for scenic apartment in big city (bonus points if food service)
Aliens always have forcefield shields
Gun noises. Enough said.
Everyone in medieval settings has perfect hygiene
Hacking = keyboard mashing on a scrolling screen of green code and suddenly you have access to the Illuminati's database
Villains killing their own minions left and right, but not even really trying to kill the protagonist(s)