Username: Carlos Castaneda

Game:
Killing Floor

Navagon

Left 4 Dead 1 & 2
Alien Swarm
Dogfighter
Portal 2
Frozen Synapse
Dawn of War 2 (all)
Killing Floor
(probably some other games too)

prakaa

L4D2
TF2
Alien Swarm
Dogfighter

Robbeasy

Dogfighter
Amnesia
Puzzle Dimension
Heretic
Hexen
Hexen DD
Hexen II

leonster929

For multiplayer, I play:
Altitude
Galcon Fusion
Quake III Arena


and under my old username, leonsterling:
Team Fortress Classic


I have a bunch of single player games, but those don't really matter for this.

I own Team Fortress 2, Left 4 Dead 1 + 2, Day of Defeat Source, Counter Strike Source, Dogfighter, etc., but my graphics card currently is SO crappy I can't really run them properly. (Despite having a very decent computer otherwise.) So once I get a new one, I'll be busier in multiplayer.

Steam Username: runehamster
(you'll note the first letter is not capitalized for added security)

Games I'm currently playing:

Not much, my current computer is terrible compared to the one I did most of my Steam shopping for. Deus Ex, I suppose, for multiplayerish stuff. $2.50 right now in Steam.

Gameace321

Games:

Sin Episodes: Emergence
Half Life 2(and Episode1)
Sin
Shadowgrounds
Jagged Alliance 2(and Unfinished Business)
Freedom Force
On the Rain Slick Precipice of Darkness (Part 1)

Multiplayer:
CSS
Half Life Source
HL2 Deathmatch
Half Life Deathmatch: Source
Killing Floor
Sin

Smannesman, of course.

And I have a bunch of games and never play anything :P
I really should start someday, but I just never get around to it.

USERNAME: TheCheese33
GAMES:
Team Fortress 2
Left 4 Dead Series
Alien Swarm
CSS
Killing Floor
TrackMania United Forever

I have bunches of other games, too, so if you're interested in playing a game with me that's not listed here, holler and I'll see if I have it somewhere in my pile of 233 games.

KavazovAngel

L4D
L4D2
TF2
CSS
DoDS

Same username as here. Send me a PM to accept you.

arcticblaster76

Left 4 Dead 2
Team Fortress 2
Dogfighter
Alien Swarm
Shattered Horizon

maxman43

I only have Deus Ex so far, don't really use Steam much.

Username: Mr. Flaming TAAAANK

Games: I'm taking a break from multiplayer games and focusing on singleplayer ones, but when I do dip into one, it's usually:

L4D2
TF2
Killing floor

Username:
adrenalinedragon

Games:
Alien Swarm
Battlefield: Bad Company 2
CSS
Day of Defeat Source
Left 4 Dead 2
TF2
Trackmania United

(got a few others but those I mainly play, depends on how stable internet is here in student accommodation)