Enemy Territory: Quake Wars

Enemy Territory: QUAKE Wars is set in the same science fiction universe as Quake II and Quake 4.

Taking place in the year 2065, the game lets you play as the GDF or Strogg in one of five unique character classes, either online or offline with computer controlled AI teammates and opponents. Employing an arsenal of weapons, vehicles and deployable armaments, engage in an action-packed test of skill and coordinated teamwork through a series of combat objectives. Persistent character growth and achievements reward players for teamwork, while clearly defined mission and class objectives guide new players to meaningful contributions on the battlefield.

Minimum system requirements: 

CPU: 2,8 GHz (x86 compatible)
RAM: 512 MB
GPU: Full OpenGL 2.1 compatible with 128 MB VRAM