Dvd.co.uk are selling "Enemy Territory: Quake Wars" for the PC for £7.95 (inc Del.)
You can get cashback through the usual places (e.g. 4% Quidco, making it just £7.63)
The next best price seems to be £9.93 from The Hut.
Enemy Territory: Quake Wars pits the armies of Earth against the invading alien Strogg in an online strategic shooter. Players choose to battle as one of five unique classes in either the EDF (Earth Defense Force -- humans) or the barbaric alien Strogg armies. Troops use 40+ conventional and futuristic vehicles, deployable structures, and defense systems like quad-bikes, tanks, and alien walkers for epic ground assaults; or helicopters and anti-gravity ships to lend firepower from the air. Throughout each battle, teams establish bases, deploy defense structures, artillery, radar, and advanced forward-command systems into enemy territory while constructing and demolishing obstacles to speed progress and gain a tactical advantage over the enemy.