Shoot zombies (or use your frying pan) and get pills.

The classic Source game, the root of Valve itself.

Shoot people to find the best gun, and possibly save a planet while doing so.

Four player Bank Heists and more.

MMOFPS, holds world record for largest single battle online.

Competitive, Casual and more, shoot and bomb your way to victory.

16 person multiplayer and long-form 4X style means games can last from hours to months.

Nine classes and over 600 hats means tons of fun.

Sandbox, Source, infinitely customizable.