Physics Blaster is an XNA game I am currently working on. I aim to release it on the Xbox Live Indie Games channel when it is complete. The goal of the game is to fire balls from the cannon and hit the target by taking advantage of physics and obstacles placed in the level. Physics and collisions in the game are handled by the Farseer Physics Engine (available here); this is a great project with lots of powerful features and I would definately recommend checking it out if you are interested in physics in XNA. The levels in the game are defined in XML files which can be created by an editor application I built for the game. These level definition files not only define obstacle positions and rotations, but also other factors such as the gravity for the level, this allows for some interesting and fun level designs. Please see some of the screenshots of the game so far with its current programmer art.