I hate people using my programs. If they didn't, no one would find bugs or downtimes and the world would be a better place.
Jokes aside ;) what annoys me a lot are people, who believe that I can solve any technical problem. While I do tinker a lot in my spare time, I am not some kind of godly being, able to turn water into wine. Just the other day, one of my friends came over to me with two laptops (different brands, different sizes, etc.) and told me: Look, that one does not work, but the display is okay, while on the other hand this laptop's display is broken. Can you please swap the displays so that I have one working laptop? Like WHAT?
It happens a lot, and most of the time, I might even be able to help, however it's the part where they assume I can do it when I tell them that I am a software engineer which annoys me.