(http://i.imgur.com/2ooLZxa.png)
There's yet another Humble Bundle option out there that will give people the chance to pay what they like for a boat load of games, all while giving to charity. This time it's The Indie Gala (http://www.indiegala.com/), and Killing Floor plus all DLC is up for grabs.
At the time of this writing you need to pay $5.91 in order to get the Killing Floor (http://store.steampowered.com/app/1250/) deal. It is currently up for sale for the next seven days.
Killing Floor is Co-op class based zombie killer game. It's unique in that the game scales in difficulty depending on how many people are in the server. Depending on what map you are playing it may be beneficial to plan out your classes in advance.
Paying only $6 for all the DLC in the game is already worth it. If you don't own Killing Floor, then $6 for the game is an outright steal, let alone all the DLC. Jump on this while you can. Killing Floor is always being played at FITES LAN events. Someone has a server up and running somewhere.
At one of our previous events Vitality Gaming had a 32 players server going. Since the number of zombies in Killing Floor scale up with each player... it was a mad house.