Pretty much the same thing everyone has said. I definitely enjoy being spanked or whipped, which is usually part of a little "game" rather than a true punishment. Part of what makes it enjoyable is the role-playing of punishment -- the idea that I've been a little bad, but I'm not really in trouble.

On the other hand, there have been a few times when I've done or said something really disobedient, and he's told me not to make eye contact until he allows it, or not to call him Master until I'm ready to treat him like one. It's never been more than a couple of minutes, but it hurts, although it is also kind of a powerful experience.