I'm really excited about Xonotic. It's the best first person shooter game I've ever played. It is open-source and cross-platform. Xonotic has a unique movement system and high variety of weapons.

Favorite games:
Xonotic    Alien Swarm     Tony Hawk's Underground
Dota 2     Super Meat Boy  Prince of Persia
Minecraft  Sonic Heroes    Batman: Arkham Asylum
Portal 2   Wolfenstein 3D  Doom II: Hell on Earth