Not precisely a game, but there has been talk lately of physics (and science in general) in games, and this is a neat little program that's fun to spend a while playing with. It's still in beta and has the requisite bugs you might expect, but here's what the creator has to say about it:
Phun is a Master of Science Theises by Computing Science student Emil Ernerfeldt for supervisor Kenneth Bodin at VRLab, Umeå University. The solver is based on work by Claude Lacoursière
Phun is meant to be a playground where people can be creative. It can also be used as an educational tool to learn about physics concepts such as restitution and friction.
You can snag the download (Windows only for now, but an OSX version is apparently on its way) at the Phun website, where there's more information. There's also a thread going over at the GameDev.com forums.