RoboWar is an open source game in which you program robots to battle each other. The syntax of the language in which the robots are programmed is a relatively simple one, based largely on IF, THEN, and simply-defined variables. Each variable attributes more to the robot's skill, and its ability to survive.
24 RoboWar tournaments were held in the past, with all contestants available on the web site. While RoboWar was originally released as a closed source freeware game for the Apple Macintosh platform, the source code has since been released and implimentations are now also available for Microsoft Windows.
The RoboWar programming language itself is based on Reverse Polish Notation and is similar in structure to FORTH.