There is a new version of Teewars! 0.4.2 with lots of bug fixes.

Get it at http://www.teeworlds.com/ (Windows, Mac, Linux)

Fast-paced sidescrolling multiplayer-only shoot ‘em up computer game. The game features cartoon-themed graphics and physics, and relies heavily on classic shooter weaponry and gameplay. The controls are heavily inspired by the FPS genre of computer games.