Topic title is intentionally vague, because the ideas I had behind it are varied.
Is there something you dislike, but have still made use of? Something you absolutely loathe in a tabletop RPG setting but used anyway because others do like it? A plot device from a movie or game and you've made reference to it in your games or fanfic? Is there a movie you despise but you watched it anyway to please your date?
It is no secret that I despise midi-chlorians. I hate that The Force was reduced to something "scientific" rather than remaining a mystical energy with a more fantasy flair. I'm eternally grateful that the Expanded Universe rarely touches the subject.
However, I am guilty of using it as an explanation in a story about my old Star Wars Galaxies RP character. At one point, she received a blood transfusion from her close friend to reverse drug-induced brain damage. Some time later, my character made a trip to Dathomir to undergo a ritual of her mother's people inside a Force Nexus, similar to what Luke did on Dagobah. However, an unexpected side effect of the ritual was a physical change in my character. She didn't grow more powerful (unless you count her senses of smell and sight increasing slightly), she didn't gain new skills, she merely changed in appearance. I racked my brain and the internet trying to come up with a plausible reason for this, since cosmetic changes via tech and chemistry are somewhat common in the Star Wars universe (such as changing your hair color via a drink instead of just dye). But in the end, I used the idea of a mutation via the midi-chlorians of her friend's blood.
I still feel dirty.
Joint Juice (and similar drinks)
I absolutely hate this nasty fake juice drink. I could get the same effects (or better, even) via vitamin supplements. But as I have the joint pains of a much older person, my partner buys this stuff to try to help me feel better. She knows I hate it, but she is honestly just trying to help and I can't be mad at her for that.
Drow and Fairies/Pixies
Personally, I love these creatures. However, one of my old DMs absolutely despised them. But he did use them in our campaigns, but only as NPCs. But he reversed his "No Drow characters" rule just for me and me alone, which made me feel honored since I knew how much he hated them.
I absolutely despise this movie. It makes me feel physically ill. But for reasons I cannot comprehend, my partner actually likes it. So I put up with it and watch it with her every once in a while while secretly wishing I could go back in time and stop the movie from ever being made.