Pronouns. I get that they matter a lot to some people, and of course it's super annoying (if not worse) to be referred to in the wrong way, but I find it unreasonable to demand being referred to something outside of the gender binary, simply because that's the way language works.
I am aware that English has used "they" for a person of unknown gender for ages, but for one, I don't think it's something that you should demand people call you when they actually know your gender, but also I really hate that this is making its way into other languages like my own, that has never had this convention. Inventing entirely new pronouns is just ridiculous, I have a hard enough time to remember your name.
I am also aware that language evolves, but this is not evolution, it's forced, and if one group of people can try to force a change they prefer, I'm as much in my right to resist it if I don't like it.
People are super passionate about this though and in fifty years I'm sure I'll be seen as a fossil for not getting with the times now - in fact I'm sure certain people see me like this now.