I got this recommendation from a friend, and I thought I'd share it with you. It's a game called RoboCode, a JavaBased API where you create your own robots that fight eachother. You can download other peoples robots from the net, and see how your own robot does. But you have to know Java to a certain degree, but I'm not talking bout a very experienced level. Actually the whole game was developed to make people learn Java in a fun way.

Looks good anyway, and I've heard it's mighty fun! Enjoy!

Here's the link