Cult of the Wind

Tomb Raider and Lost Planet 3

Super Monday Night Combat (aka Super MNC) is unfortunately :(

Day of Defeat, killing floor, deathmatch classic, Half life deathmatch.

Day of Defeat, killing floor, deathmatch classic, SMNC, Half life deathmatch.

Tomb Raider Multiplayer, Section 8, Nuclear Dawn, Nexuiz, Brink, Max Payne 3 Multiplayer, Post Apocalyptic Mayhem, Special Forces: Team X, Dungeonland, Lead and Gold, The Ship, ...

Ravaged: Zombie Apocalypse and Rekoil.

Shootmania if you are from America. Not much better in Europe though.

Unreal Tournament 2004.

So loved Onslaught mode on it, was the sniper.

The Showdown Effect.

Arkham Origins

Secret Ponchos

Strike Vector D:. R.I.P most awesome game ever.

Clickr, though that MP is mostly dead because of the bug that crashes your game if you play more than one MP game. A shame the dev never fixed it because MP in that games is really fun.

Painkiller (the ones that have multiplayer), also Shattered Space.

Monday Night Combat :(

Orbital Gear

NEXUIZ

Tomb raider dead space 2 and bioshock 2

Quake Wars.

Gun Monkeys.

http://steamcharts.com/

Blacklight: Tango Down