Xonotic

Xonotic is a fast and furious open-source arena shooter designed for players who think ordinary first-person shooters move far too slowly. Built around classic arena combat, it emphasizes speed, powerful weapons, vertical movement and maps designed for constant confrontation. Matches can become spectacularly chaotic, with players bouncing around the environment while collecting weapons and power-ups and attempting to turn everyone else into a statistic. The game's open-source nature has allowed a dedicated community to develop and maintain it, giving it a distinctly independent character. Fans of Quake-style multiplayer shooters will find plenty to enjoy, especially if they miss the days when FPS games were less concerned with cinematic realism and more interested in seeing how quickly a rocket could ruin someone's afternoon.