Garry's Mod

Garry's Mod (commonly abbreviated as GMod and typecased as garry's mod), is a sandbox physics game created by Garry Newman, and later by his company, Facepunch Studios for Microsoft Windows and OS X. Garry's Mod was originally a mod for Valve's Half-Life 2, but was later made into a standalone release in 2006.

Although Garry's Mod is listed as a full game, it has no objectives and instead gives the player a sandbox to manipulate items free of restrictions, although most multiplayer servers offer original game modes created by players. Garry's Mod allows players to manipulate items, furniture, and props – various objects that players can place in-game.

More information: 
Available servers: 
garrysmod.liquid.gamersnights.com:27015