My Swat LOVES to have his tummy rubbed. He will lay like this for hours, as long as we keep rubbing his tummy. Let's see all those pretty kitty tummies.
A lot of cats take it as an invitation to wrestle, which involves teeth and rabbit kicks and claws, at least with mine. He does that if I try to rub his belly when he's awake and playful. However, sleepy Oliver LOVES belly rubs. He'll twist and turn to get rubs all over, but he ends up on his back purring for belly rubs. And when I stop, he wiggles to remind me he's still there... wanting more belly rubs. I'll have to get a pic tomorrow.