Killing Floor brings old school fun at a reasonable price.
Killing Floor is a first person, co-op game by Tripwire Interactive (TWI), makers of red Orchestra. It was originally a mod for UT2K4 released in 2005, until TWI bought the license and released it as a full game.
You play against increasingly hard waves of zombies (how many waves can be decided by the host, but long games consist of 10 waves and can take up to 45 minutes to complete) along with 5 other players trying to survive and defeat the final boss, know as "The Patriarch".
You can also equip perks, there's 6 in total and each give you a certain advantage with a certain type of weapon or equipment (like faster use of medicinal syringes or waster welding, yes, you can weld doors). Perks are persistent through servers (as long as they are running with official mutators) and they level up (being 5 the maximum levle you can achieve), giving you higher bonuses as you progress through the game.
Teamwork works a little different than say, Left 4 Dead. In fact, both games are completely different and should not be compared as they focus in different aspects (L4D focus in characters and narrative where KF is about guns and blasting things away).
But it is worth nothing that even if you are required to help your team you are not forced to adopt this as a full time job, which allows the player to explore the area as they see fit.
KF also features "ZED-Time", which randomly slows down the game whenever you make a nice kill.
Personally, I thought I was going to hate this feature, but it turned out to be my favorite thing about the game.
If you are the one triggering the event, you'll be rewarded with a sweet death scene and body parts flying all over the place in slow motion. If you are not the one triggering it though, you can still use this moment to watch around or catch your breath.
The best thing about the game is probably it's weapons.
KF features 16 guns, all of them are different, balanced and useful against different types of enemies.
Guns behave in a very realistic way, you don't have a crosshair (but you have iron sights) and they have great sounds as well.
Enemies are nicely varied too. As you survive you'll encounter a larger variety of zombies on each wave forcing you to change your perks, guns and play style to match the odds, making the game fell a bit more dynamic than it would seem at a glance.
Graphics are a bit outdated, and they should be as it's running on the UT 2.5 engine. But this is compensated by a great art style (which is very dark, moody and reminiscent to old games like the first few Resindet Evil and Silent Hill games), fantastic weapon models and some nice details here and there (flashlights look hedious, but being able to see your teammate's lights not only aids the gameplay but it also adds to the immersion a lot too).
Overall, I love this game. It's NOT for everyone, and I think that L4D fans might not like it.
It is certainly not as refined as many other games (it also has the worst looking, yet functional menu I've seen in a game in years) but what it lacks in presentation it makes up in fun factor. And that's all that mathers.