Following the Mann-conomy update, TF2 is now on sale until Monday, Great game, it's got some nice servers that are located in Australia and Valve is always updating it.
Team Fortress® 2 (TF2) is the sequel to the game that put class-based, multiplayer team warfare on the map. This year's most anticipated online action game, TF2 delivers new gametypes, a signature art style powered by Valve's next generation animation technology, persistent player statistics, and more.
Unlike other "class-based" games that offer a variety of combat classes only, Team Fortress 2 packs a wild variety of classes which provide a broad range of tactical abilities and personalities, and lend themselves to a variety of player skills.
Play as the flame-throwing Pyro, the room clearing Heavy, or the Spy, a master of disguises. Other classes include: Scout, Sniper, Medic, Engineer, Demoman, or Soldier.
TF2 features the most advanced graphics of any Source-based game released to date - and the most exciting class-based action ever created.
Good deal; awful update.