TripleA - TripleA is a free (under GPL) turn based strategy game based on Axis & Allies board game.
LaTale - LaTale draws heavily from some other 2D side scrolling video games to provide a great fantasy MMORPG world.
Domination - Domination is a game that is a bit like the well known board game of Risk.
Dungeon Fighter Online - Dungeon Fighter Online is a Free-to-play, Massively Multiplayer Online, Role-playing, Action-Adventure, Hack and Slash, and Fighting video game created and published by Neople.
ThumbZilla - Awesome thumb stomping and kicking action game.
NosTale - NosTale (The Tale of Nomads of Silver Spirit) is a totally free MMORPG that includes simple (but beautiful) graphics and also lots of class options.