TORCS, The Open Racing Car Simulator is a highly portable multi platform car racing simulation. It is used as ordinary car racing game, as AI racing game and as research platform. It runs on Linux (x86, AMD64, ARM and PPC), FreeBSD, OpenSolaris and Windows.
Imperium Mundus is a real time strategy game written in pure Java (Java 2 SDK 1.4.2). The game objectives are many: hold your own territories, capture enemy territory, establish or join strong alliances, conquer the whole world or just try to survive.
Alfaws is a customizable, multi-user game engine. Every object, character, & room is programmed to respond to events. Players can customize their own event handlers, thus changing their fighting style or having their character behave as they would.