This was a game a worked on in my spare time one semester. I never got around to finish it, but I still think it's interesting enough to mention here. It was made in Java and uses box2d for physics, which means you can interact with objects such as boxes and bullets on the ground.

Basically it's a singleplayer, top-down, 2D shooter. The idea was to have various goals such as eliminating all hostiles, rescuing hostages and possibly others. The prototype featured multiple weapons, multi-layered graphics, AI-controlled enemies and power-ups.