If you own Half-life 2...

[wethepeople]

GET Zombie Master. Its a zombie mod for the game that freaking rules. 15 or so survivors load up into player made maps and have to complete objectives and most importantly... survive. One player controls the game RTS style with their zombies, and summons legions of creatures to fight the survivors. Many intense moments include you and your group getting surrounded in a hall full of zombies with no way out, player set traps killing everyone but you, etc. The mod is free and it owns. Its like the new Left 4 dead except with custom maps and 16 players instead of 4. Nothing like having to hold a 100% physics driven house from a horde of zombies for an hour. Blocking windows with crates, boards, tables, etc. Finding shelter and guns, it just owns. @_@ GET IT.