Something that makes you annoyed as hell when it really shouldn’t, or something that makes you feel like a 
for getting annoyed at it.
I’ll start with a combination of the two: When people call chiptune music “bitcrunch”
When people get too sexual while playing DnD. I don’t care if ur a bard, if u try to push my beautiful autistic DM into describing ur fantasy I’ll kill you in ur sleep.
My current rpg (playing Fate and not D&D, but still) has two clear rules from session 0: No foregrounded sex, no foregrounded gore. I also did a “And let’s move on” when one of the players was trying to flirt his way into a bar.
It’s been working pretty well so far.
People who whistle. I consider myself a reasonably calm and understanding person, slow to anger. But something about people who whistle just sets me off instantly.
