Any show that starts with someone walking in on the aftermath of some event, and then all the other characters tell their own self-aggrandizing versions of what happened.
One of the main characters meets a close relative he never realized he had (e.g., Homer’s half-brother Herb Powell on The Simpsons, and Hank Hill’s half-Japanese half brother on King of the Hill). These relatives appear in no more than one or two episodes and then are completely forgotten.
There was an episode of BUFFY that handled this trope very well indeed (primarily by setting it up as an “evil twin” story and then revealing that it was not so).
When one person is deceiving the other person in the relationship about who they really are, and s/he’s about to tell the other person, but is interrupted, and doesn’t bother trying again, and then the other person discovers it on their own, gets pissed off, and finally the deceiver convinces them of their true love.
Any seen where they disarm a bomb while the clock ticks down. This is a scene that is supposed to be dramatic, but we all know they will succeed (unless it is a guest star) with 001 left on the clock.
I thankfully haven’t seen this one in a while, so maybe the concept is on the shelf for now, but I used to get very annoyed about the scenario where the guy would somehow get talked into having dates with two different women at the same restaurant. Hilarity ensued as he would constantly get up and run between tables to try and get away with it.
Mentioned earlier, but I’ll elaborate: The one where the pregnant woman and the teenage doofus get stuck in an elevator. Something about being stuck in a sit-com elevator always causes pregnant women to immediately give birth and it also causes teenagers who can’t find their own behinds with a road map and a flashlight to suddenly develop obstetrical skills.