XreaL is a heavily improved Quake 3 Arena engine. It's bundled with new tools and a demo game that was never finished. ET:XreaL is a subproject bringing all XreaL enhancements to Return to Castle Wolfenstein: Enemy Territory.
Command line tools helping you to create bzflag map world files with complex objects like trees, bridges, block pyramids, minefields, tunnels and so on.
Written in python2.2 (linux). Screenshots -> Home Page! Play demo map at ducati.bzflag.org:5157.