when people assume you're upset/pissed off just because you're being quiet - not everyone is loud and extroverted 24/7
(related is what someone else mentioned about people talking to you when you're reading/have headphones in)
If you know the person well that can be a sign they're not feeling normal. If they are quiet in class, movie, or something then it's understandable.
On a related note, I hate my classmates at college. They assume I'm so quiet and never talk because I sit there a listen to what the professor has to say. I may not even say a word the entire class, unless someone ask me something or I have a question. I believe there's a time and place for everything. I'll be myself outside of class and be serious in class.
When parents name their kid a name, like Johnathan, but call the them John. Why the fuck didn't they just name him John if they're going to call him that.
People that live and breath texting.
Girls that are too flirty