So, I'll recommend a game, and this might turn into a mini-review, but that's kind of what this thread is about.
So, I just bought Killing Floor. A game that I knew was good, a lot of people like it and such - but I didn't quite know just how good it was. So it was and is still on sale, for 75% off till Nov 6th. So I picked it up with a bunch of other games for 5 dollars.
So, I downloaded the game from Steam and started playing it online. This game is based around 6-player co-op survival. You enter the game with about 10 seconds till the 'round'/wave starts. You have a 9mm Pistol that does relatively well against all the starting enemies especially if you get headshots.
There are 10 enemies in the vanilla game, the Clot which is a relatively weak and slow zombie, Gorefast which is like the clot but has more health, runs at you faster after it gets close enough too you, and has a sort of metal blade for an arm that it attacks you with. Then there's the bloat, which is huge and fat guy that spits pretty much acid at you but is only really dangerous at very close range and are relatively weak. Next is the Crawler, which runs around on four legs and is faster than most enemies and can leap at you. Very weak though.
Next is the Stalker, which is a weak but highish damage enemy that goes invisible until it gets close enough to attack you. Only thing is, it's actually pretty damn easy to see them so they aren't very dangerous unless you're getting swarmed by other stuff as well and you don't see them. Then we have the Siren, which is a slow walking zombie woman who when gets near enough to you, screeches with red waves coming off all around it doing a pretty good amount of damage over a small amount of time. Not too dangerous, usually get picked off before they get to you but can be dangerous if swarmed like the stalker.
Next we have the Scrake, which is your first truly dangerous enemy. These are very resilient enemies that walk towards you until they get close enough, then they charge at you and try to attack you with their chainsaw arm. Very dangerous and if you don't have the right weapons you can get killed by one pretty easily. Though if you're playing as the marksman, you can usually get the crossbow before they come, and the crossbow will kill most enemies in 1 shot to the head, including Scrakes. You'll soak up the kills on all the specials with one of those 
Next is the Flesh Pound, this is the most dangerous enemy that will come after you other than the patriarch. The flesh pound is a large specimen (Yeah, the 'zombies' are all called specimens... so that's what you call them, since most of them aren't really zombie-like) that has a yellow light on it's body. If you cause too much damage in too little time, and especially if shooting him with small weapons, he will become enraged and charge and whoever attacked them the most unless that player is very far away (Making it easy to get your friends killed if you're a sniper on a large and open map ) He is highly dangerous with 2 metallic giant screw sort of arms that rotate when it attacks you, extremely dangerous, only takes half damage from bullets and takes extra damage from explosives. Most people don't know that though
Next is the Husk, which is relatively common but not too dangerous. The Husk looks a lot like the Flesh Pound but he is a ranged attacker, the only one other than Patriarch. He has a rocket gun as a hand and he fires these at you, these aren't particularly damaging but they do set you on fire and you can be in trouble if also being attacked by other things as well, it's also really annoying to be finished off by one of these while healing yourself.
Last is the Patriarch. The Patriarch is the boss at the wave after the last (So there is 1 more wave than you think) He has 1600 health, can cloak to heal when he gets too damaged (And he goes completely cloaked, and you can only see where he is if you set him on fire) during which enemies will attack. He has a chaingun and rockets and is extremely dangerous, easily taking out at least one person with one chaingun firing sequence if you can't find cover. Extremely easy to get shot at the last second before you can get into cover.
Now to the other parts of the gameplay. There are perks as well, but they aren't what you think - Each perk is based around certain weapons, as you progress by usually either killing a certain number of zombies with your weapons, doing damage with your weapons, or getting headshots with your weapons depending on the class you progress to Level 6 in your perk. Choosing a perk allows you to have discounts on your class/perk's weapons, maybe do more headshot damage, and even eventually start off with a class-specific weapon that isn't your 'crappy' little 9mm pistol. There is Commando (Assault Rifles), Marksman (Pistols and Snipers Rifles and regular rifles), Firebug (Flamethrowers and stuff), Berserker (Faster walking and melee weapons), Field Medic (Better healing and armor, as well as Medic guns that can shoot as well as heal other players from a distance rather than the little medic shot tool that everyone has), Demolitions (Explosive Stuff, Grenade Launchers), and Support Specialist (Shotguns).
At the end of each wave you go to the trader where you can sell and buy armor, weapons, grenades etc. There is a large amount of weapons to choose from and with the perks you will have something to go for while using the differant weapons. Also, if you use weapons from other perks you can progress in those perks, but you won't get the benefits if you're not using it. So you can still use all the other weapons, they're just more expensive and less effective. So you go through the rounds, earning money and possibly sharing it. The whole time you're playing you're playing with up to 6 players.
Now that's about the gist of the vanilla game, but lets delve into mods.
The first mod I used was KF Gun Game. This adds a competitive mode where you can fight other players in the Gun Game game-mode which you should be firmiliar with from quite a few modern FPS. It's very fun there seem to always be at least 2 servers with a few people in them so it's still pretty active. I really recommend the mod, it's a nice way to Spice up the game. There are also a variety of other mods as well as new gun mods that are great, a good few able to be downloaded from the Steam Workshop.
Next is my favorite way to play Killing Floor. Endangered's Killing Floor Server. This server is extremely modded with new perk stuff and going up to level 60, as well as tons of new enemies, more than tripling probably the weapon amount, and up to 20-25 players at a time with lots of extra hard enemies and sweet new guns. Once you get past all the download time you'll find a ton of new content and maps. Extremely fun, though if you're computer's kinda crappy or your internet connection is, you may have some problems but try it anyway. It's super awesome.
So yeah, there's my Mini-review/maybe fully-fledged review on Killing Floor so far, oh. And don't buy the Community Weapon Pack. Fucking rip-off, you can play with all those weapons on the Endangered Server anyway 
Maybe you died alot and got frustrated and quite...lol