I get annoyed when, just because I'm female, I'm immediately supposed to know everything about girls and women. Some examples might include anything about relationships, make-up, gossip, fashion etc. It bugs me to no end, especially as I most of the time have no clue why your girlfriend is mad and hasn't called you back.
I don't get the thank-you card thing, either, but I've gotten better at writing them thanks to my mom. She used to have to beg me to write them. While I still don't really see the point, at least I'm in the habit now.
Also, it's really annoying when people say one thing, and they really mean another. If you want to say something, say it directly. There's no need to run circles around the issue and get mad when I don't follow. I wish people would be more honest.
i only know what i know... but yeah, people seem to think that one woman speaks for all women. Silly, really...