What's an innocent misconception about your hobby/profession that drives you up the wall?
Like for example, how someone thinks because you work in IT you can fix their TV, or how if you're into music you must be able to play any random instrument.
I just like hearing pros rant about about their very niche problems.
I'm an English professor, and I get a lot of "Oh, I'll have to make sure to use good grammar around you." First, I have better manners than to go around correcting other people.* Second, I know enough about the development of the language to realize how fluid and often artificial the "rules" are.
Unless you're trying to mansplain something to me. Then all bets are off.