Killing Floor was a disappointment. Largely a "me too" game that was released some time after the 2008 zombie survival title, Left 4 Dead, it fails at every turn to be interesting.
Where Left 4 Dead was about making it from point A to point B and surviving everything in between, Killing Floor is about staying in the same place and surviving wave after wave of zombies. You will mostly be hunkering down in a room and killing monsters as the flood in, and you are given the ability to reinforce doors, heal others, and a few other abilities based on what class you choose to play.
By now you should know the drill. There are hordes of zombies and other undead things that want to kill you. Your goal is to survive. The problem is the game doesn't amount to anything beyond huddling in a room with a bunch of the other players staring out a doorway waiting for the siege to happen. Maybe you'll be the guy that reinforces the door. Your job is to stare at the door and hold down your mouse button. Or maybe you will be the guy with the sword. You know, the useless guy who thinks he is being helpful and super-skilled by engaging in melee combat. Or maybe you'll be one of the many people who huddles in the corner, randomly jumping and crouching, while swiveling your mouse around nervously, looking for something to shoot.
The game looks like puke, even for a game that is 5 years old. It already looked old upon its release, and it has not aged well one bit. The games sounds can be impactful at times, but the recordings of monster sounds vary in quality and are largely as scary as a cassette tape with spooky sounds on it, the kind you hear during Halloween. But the game is just mechanically a mess. Hitboxes don't feel right. Sometimes you will go to make a shot where you clearly would have landed the shot, but the guard rail in front of you might look like you cleared it, but in actuality, the game registers it as having hit the guard rail. The zombies move jerkily, and this isn't because they are animated to do so, nor is it a hardware issue on my end, but rather, the game does not have smooth movements of its characters. Monsters can will themselves to fly, ascending the edges of even the smoothest geometry. There is a shop in the game where you can buy ammo and weapon upgrades. Reinforcing doors is a necessary evil. You almost must do it to get through the later waves, but it is patently boring for the reinforcer. But even other roles are not all that interesting. But if your idea of a good time is to sit in one place staring at an unchanging environment as you slowly fight off an inevitable death... wait... woah, Killing Floor is pretty meta for a hardcore gamer. But I digress!
Killing Floor is visually bad, audibly bad, and mechanically bad. It was bad in 2009 and here in 2014 its still bad. If for some reason you have found your way to this review for some unknown reason, take my advice and save your money. Even if Killing Floor was free it wouldn't be worth your time.