Counter-Strike - Counter-Strike is a PC-exclusive FPS video game developed by Valve Corporation.
Blockland - Blockland is a non-competitive multiplayer sandbox-style construction game. It's kind of like playing with legos on the internet.
Xonotic - Xonotic is a free (GPL), fast-paced first-person shooter that works on Windows, OS X and Linux.
Garry’s Mod - Garry’s Mod is Funny, Sandbox, Co-op, Building, FPS, Action, Single and Multiplayer video game created by Facepunch and published by Valve.
Rage - Rage Software, also Rage Games and FX Digital Network, was a British video game developer.
Roblox - Reimagining the way people come together.