Lugaru is a 3d martial arts fighting game that mainly plays in open-air levels in it's proprietary version. Besides kicking and jumping, sneaking and weapon use are main features of the game.
A fork allowed me to compile Lugaru on 64bit Linux with ease.
Hopefully tutorials for creating completely original content will appear soon, so there can be some fully faif fun foon (soon) with fully free content, for example with a gnu fighter from Ryzom.
Lugaru open source main menu, if you add the proprietary content