MMO
A massively multiplayer online game (also called MMO and MMOG) is a multiplayer video game which is capable of supporting large numbers of players simultaneously. By necessity, they are played on the Internet. Many games have at least one persistent world, however others just have large numbers of players competing at once in one form or another without any lasting effect to the world at all Read the full article at the Wikipedia.
Tale of Toast
With its easy to pick up play style, open world player versus player with high stakes for those daring to partake, and its focus on...
Genre: MMO, Adventure 
Albion Online
Albion Online is a sandbox MMORPG set in an open medieval fantasy world.
Genre: MMO, Role-playing 
rpgtest
by cd2
Rolling release
(20 Dec 2015)
Rpgtest is a voxel-based game which incorporates elements from RPGs and sandbox games.
Genre: MMO, Role-playing 
StarBreak
(10 May 2016)StarBreak is a unique skill-based action platformer MMO where you explore strange sci-fi worlds alongside dozens of other players,...
Genre: MMO, Adventure, Action 
BattleStick
by Pinterac
(6 May 2016)
BattleStick is a crazy and casual fast-paced physics-based 2D stickman MMO where you fight others in an arena with several weapons...
Genre: MMO, Action 
Strife®
by S2 Games
(22 May 2015)
Strife® is a truly free to play, competitive, online ARTS / MOBA that features non-stop action and engaging combat.
Genre: MMO, Strategy, Adventure, Action 
Pandum
1.11.18 (25 Jan 2018)free to play cross-platform MMORPG with arcadified gameplay
Genre: Arcade, Beat 'Em Up, MMO, Social, Role-playing 
Source of Tales
This game initially started as our entry for the Liberated Pixel Cup 2012.
Genre: MMO, Role-playing 
Meridian 59
Meridian 59 is a long-running medieval fantasy combat and adventure MMO, and was the first commercial 3D MUD upon its release in 1995.
Genre: MMO, Role-playing 
Catch Challenger
This game is a independent MMORPG, Lan game and a single player game.
Genre: MMO, Role-playing 
Les Landes Eternelles
Les Landes Eternelles is a french fork of the project Eternal Lands.
Genre: MMO, Role-playing