Pet peeve: people who assume I mean something else.
Example: I say, “Type richardbarron.net in the URL window.” They answer, “Do you mean richardbarron.com?”
This is a good reason to just outright hate people. It’s not that the individual person who answered is all that contemptible, so much as the fact that people in general are so lax and imprecise with their communication skills that clear, direct statements are ignored or distorted all the time.
The next time someone asks me, “Do you mean…”, I’m going to tell them, “I said what I meant, dickwad!”