Silverlight TruckWars is a real-time strategy game built entirely in Silverlight. I recently releases version 1.2, with the big feature being that it uses the Farseer Physics engine. I also simplified the game play, and added some new creatures. I'm trying to move the game from "technical gimmick" to "fun".
Ultimately I'll try to open-source it so others could create their own creatures and levels.
About the game play - I had feedback that the previous physics engine (some scrappy code I had whipped up) just wasn't powerful enough to do what I wanted. I want the game to be about interacting systems - like trucks colliding with each other, growing objects (that change their size), pushing around crates, bouncing bricks that can crush a unit if they overlap, etc... All of this requires a powerful physics engine, which is why I took the effort to migrate to Farseer.