In this thread you can post about any free game that you like, and I'll update the thread every time a new game comes up.

Team Fortress 2
"One of the most popular online action games of all time, Team Fortress 2 delivers constant free updates—new game modes, maps, equipment and, most importantly, hats. Nine distinct classes provide a broad range of tactical abilities and personalities, and lend themselves to a variety of player skills!"
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Rusty Hearts
"Rusty Hearts is a multiplayer online game with fast-paced and highly-stylized brawling combat combined with a solo or team-based dungeon exploration experience. In this gothic inspired world of vampires, half-vampires, and humans, players will be able to unleash devastating combo attacks, engage in a wide variety of epic monster battles, collect valuable loot, and become a unique hero."
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Cave Story
Cave Story is one amazing game with an NES-style feel to it. The only creator of this game calls himself Pixel, and it took him over 5 years to develop- I'm sure it was worth it!
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osu!
osu! is a rhythm game. There's four modes to choose from- CatchtheBeat being my favorite. An overall great community (although sometimes they get on my nerves with all their anime), this is by far one of my favorite games to spend time on.
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Torus Trooper (scroll down a bit for the download link)
"Drive a ship forward and destroy enemies. When time runs out, game is over."
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NetHack
"NetHack is a single player dungeon exploration game that runs on a wide variety of computer systems, with a variety of graphical and text interfaces all using the same game engine. Unlike many other Dungeons & Dragons-inspired games, the emphasis in NetHack is on discovering the detail of the dungeon and not simply killing everything in sight - in fact, killing everything in sight is a good way to die quickly. Each game presents a different landscape - the random number generator provides an essentially unlimited number of variations of the dungeon and its denizens to be discovered by the player in one of a number of characters: you can pick your race, your role, and your gender."
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Dwarf Fortress
"Dwarf Fortress is a single-player fantasy game. You can control a dwarven outpost or an adventurer in a randomly generated, persistent world."
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It's probably not what people are expecting on this thread, but I think Snailiad is a really fun Metroidvania-style game. The big twist being that it's (obviously) about snails, which is adorable. You even regain health by nomming on plants! Of course, it's not multiplayer so it doesn't have tons of replay value, but if your a fan of its genre (or snails), I think it's a gem that's worth at least a try.

Another game I really like on that site (not advertising, I swear) is Icebreaker. Nitrome actually has a game on Steam Greenlight (basically, where Steam posts a demo of a game to see if people are interested enough to warrant putting the whole thing up for sale), and I think they've displayed the same professional effort here. It's a 2D physics-based puzzle game, if you're into that sort of thing, which I'm sure plenty of you are, and it's about Vikings!

Beneath a Steel Sky: http://www.gog.com/gamecard/beneath_a_steel_sky

A fun point and click adventure game. Lots of puzzles, great story, and loveable characters. Definitely a must play for any fan of the genre.

Tribes Ascend: https://account.hirezstudios.com/tribesascend/

Fast paced first person shooter action! Players may use the "ski" ability to move at an incredible pace. Jetpacks are used by players to fly and perform great jumps when moving at highspeeds. "9 playable classes, unlock and upgrade weapons, three different vehicles to use, and open battlefields." Also, unlike in most FPS, you must account for distance when taking your shots in this game as your shots will not travel in a straight line.

A retro multiplayer shooter

Teeworlds is a free online multiplayer game, available for all major operating systems. Battle with up to 16 players in a variety of game modes, including Team Deathmatch andCapture The Flag. You can even design your own maps!

Sonic Robo Blast 2 and Mari0.

osu! is one of my most favorite games on the computer.

Who can have a list of free games without:

Slender - Slender is a first person horror game where the main objective is to collect all 8 pages before Slenderman kills you.

I wanna be the guy! - An impossible platformer about a MegaMan like man who wants to become The Guy.

Alien Storm - A top down shooter developed by Valve with amazing co-op gameplay.

Kingdom Rush  - http://kingdomrush.com  - ToD/Strategy
For all you ToD (Tower of Defense) nuts out there, this game brings a slight RPG twist to the genre. It's fun and will keep you occupied and entertained for HOURS. So much to do and tactics and strategy is a must! Simple Storyline.

Demons vs Fairyland - http://armorgames.com/play/14430/demons-vs-fairyland - ToD/Strategy
Again, like Kingdom Rush, this is a RPG-like ToD game. But, the Storyline is so cute and surprising at the end!!! I do warn you though, this is a lot more challenging than Kingdom Rush!

Being One Series - (Can we post Mature rated games on here?)



(I'll edit my post once I find more games )

CAVE STORY CAVE STORY CAVE STORY CAVE STORY CAVE STORY... I love cave story and yes I said it a lot I got the best ending by fighting ballos (Took me about 10 days) And I got all the endings all modes too. Well.. On the wiiware verison

Probably a lot of you have never heard of this one, but Ikachan is a good game. It's from the makers of Cave Story(still need to play it), and it's a small RPG that I find to be quite a nice game. You can find it here: tinsanity.net/ikachan ya'll should give it a try!

all your game needs... shows you all games   http://mmohuts.com/

MapleStory, Spiral Knights, Realm of the Mad God, Cosmic Break, Rumble Fighter.

Digital: A Love Story is like a novel and may be nostalgic to those who owned an Amiga when they were younger. You explore BBSes (Bulletin Board Systems) and get into all kinds of crazy antics. http://www.scoutshonour.com/digital/
mari0 is the original Super Mario Bros... except with PORTALS! http://stabyourself.net/mari0/
Also from the creator of mari0 are Not Tetris and Not Pacman which are your favorite classic games modified to have physics. http://stabyourself.net/notpacman/ http://stabyourself.net/nottetris2/

A good free game is Istunt2 for the android phones or iPhone, it's fun and entertaining and its about snowboarding.

A really great, and up to date game for many players is Dragon Nest by Nexon. It's a fast action multi-player fantasy/ action RPG, with fantastic graphics, PVP tournaments, Free giveaways and more! You'll meet tones of great people, to chat and play along with. Definitely worth the
4 gigabyte download required to play

You can play by yourself or with a party of friends, join a guild and become an unstoppable force.

Choose a class and jump right in. http://dragonnest.nexon.net/guides/class-guide#warrior

Don't forget to download http://dragonnest.nexon.net/support/game-download

http://nxcache.nexon.net/dn/img/guide/questing/tn-4.png

One of my favorite free PC games that I would like to share is... Ib.  

Ib is a horror/adventure game created by Kouri. (Translated to english by vgperson.)
You play as a young 9 year old girl named Ib who visits an art gallery with her parents.  Things turn for the worse when suddenly the gallery comes to life and she is trapped in it's twisted world.  

One play-through is about 2-3 hours but it has multiple endings so there's plenty of replay value.

The official page isn't working atm so I'll post the tumblr download page:  http://vgperson.tumblr.com/post/45899474594/ib-1-04
Enjoy!

What about "Final Combat" anyone play or hear anything about it other than it is a rip off of "Team Fortress".
It looks comical enough to try.

http://www.youtube.com/watch?v=rp4R7gd3fxU

I wonder what the final verdict is on that thing.
If it is too taboo to mention rip off's then forget this post and move on.

Good Luck To All.
Peace.

One that is fun to play with friends (Especially competitive friends is Star Conflict

It is a highly addictive team based space shooter.

Thanks for the ideas everyone. You guys are really awesome to sit down and take the time to give us all gamers info like this. Vindictus, and runescape are awesome free games, also star wars the old republic went free not to long ago. ENJOY!