I haven't had one in session, but did have one journaling about a session. I told t about it and we used the writing to explore some issues. I was doing some stream of consciousness type writing about a difficult session. In my head I wrote "I tell you what you want to hear." On the paper I actually wrote "I tell you what I want to hear." You can imagine the kind of discussion that led to. It was one of those therapy light bulb moments.