Because I never know what to expect in a session, I am constantly surprised by moments or activities in some way so I could probably write a book on the subject. Therefore, unlike what I normally do I will try to keep this answer brief and just pick one.

My largest surprise had to be the time where my Domme decided that we should switch for a session so she had me lay down on the medical bed with my eyes closed. Meanwhile she did some self-bondage with rope where she hung herself from one of the hooks in the ceiling. When she was finished, she told me to open my eyes and I was so stunned that I literally didn't know how to react for a full minute (she told me later she started panicking a little when I laid there in an almost uncomprehending fashion before I finally got up and came over to her).