Problematic question. I know generalisations are fun, but there is no one thing that all women do that bothers me. Just when I think I found something, the woman I'm with proves to me that it was a misconception on my part. But, as we're playing at generalising everything, let me give it a go:
Use phrases like, "It's nothing," and "I'm fine," when those phrases clearly aren't true.
Women have the ability to make everything the fault of someone else.
Women use PMS as an excuse to be a bitch.
Generalisations are fun!