Ooooh, good one ID. It IS all about the fun!!
Of course, playing is fun. That's why we call it "play." What I find the most fun is pushing limits. Trying new things, going further, its all great.
I also enjoy trying to push the limits with Sir. As anyone who knows me will tell you, sometimes my mouth gets away with me. But when I come out with something particularly cheeky, and He is laughing too hard to punish me, it is great fun.
....although he usually remembers and punishes me some time later.....but that is fun too!!