So my friend Don has been learning iPhone/iPad programming lately, and he decided to implement a pong game to learn how to do game and graphics programming. He'd done this before, years ago in DOS, which makes it a good task to learn the new API.
He kept showing me code... and of course that got me thinking.
You may now be saying, "But wait! Pong doesn't need a physics engine!" Yes, yes, you're right. The world doesn't need yet another pong game either. But I did want to learn to use box2d anyway, so I'd call this a success.