Yohoho! Puzzle Pirates

Yohoho! Puzzle Pirates is an addicting 2D MMOPG (MMO Puzzle Game) from Three Rings Designs. The game offers both free game play, and pay options. In addition, it offers International Seas (Servers) and is available for Windows, Mac, and Linux. Finally, the game offers full-screen and window gameplay.

Gothic 3

Gothic 3 is a fantasy-themed role-playing game for Windows from the German game developer Piranha Bytes. It is the sequel to Gothic II. Although widely available in English, the native release of the game is German.

Cube

Cube is an abstract sci-fi FPS game for the PC from 2002

Bang! Howdy

Bang! Howdy is a 3D online strategy game, in a steam-powered wild west world, from Three Rings Designs. It is available for Windows, Mac, and Linux; and offers full-screen and window gameplay.

Second Life

Second Life is an online virtual world developed by Linden Lab which was launched on June 23, 2003. A number of free client programs called Viewers enable Second Life users, called Residents, to interact with each other through avatars. Residents can explore the world (known as the grid), meet other residents, socialize, participate in individual and group activities, and create and trade virtual property and services with one another. Second Life is intended for people aged 13 and over, and as of 2011 has more than 20 million registered user accounts.

Vanguard: Saga of Heroes

Vanguard: SOH is the MMORPG from Sigil Online. Unfortunately it is no longer online.

Half-Life 2: Episode One

Half-Life 2 is an FPS from Valve Software, and was one of the most highly anticipated sequels of all time. You return as Gordon Freeman, the strong and silent-type physicist, and you must do battle with an alien race of enslavers to liberate the surviving remainder of humanity on earth.

Hero Online

Hero Online is a completely free MMORPG. Free to play, and free to download

Clive Barker's Undying

Clive Barker's Undying is a horror-themed FPS from Dreamworks and EA Games. The game takes place in an immense haunted estate on the coasts of Ireland in the early 20's. You play as Patrick Galloway, a man with limited supernatural powers who served in WWI, and must investigate a curse that has, one by one, caused every member of the aristocratic family to be driven to madness, and reanimated as a demonic monster upon their untimely death. Groundbreaking horror author Clive Barker was a consultant in the game's plot and background story, and also provided the voice for one of the antagonists.

Project I.G.I.: I'm Going In

Project I.G.I.: I'm Going In (released in Europe as simply Project I.G.I.) is a tactical first-person shooter developed by Innerloop Studios and released on December 15, 2000 by Eidos Interactive. It is one of the first computer games to feature realistic weaponry and tactical combat situations.