The Atomic Game Engine features 2D and 3D rendering, standards compliant JavaScript, full Player and Editor source on GitHub, Windows & Mac Editors, with deployment to Windows, Mac, WebGL, Android, and iOS from the editor. The standard version is Free.
Valhalla Game Studios has announced Devil’s Third Online, a free-to-play PC version of Devil Third’s multiplayer. The game (should) release Q4 2015.
Mechanic Watermelon is a RAGE Action-Platformer-Puzzle game. For windows, linux and mac.
This is a short 1 playable level demo. Final Fantasy VII: Re-Imagined is a non-profit project made by fans of the original game. Final Fantasy VII re-imagined as a 2D action side scroller.
Unending Galaxy is a top down 2D sandbox, simulation and strategy game based in space. The game allows you to play at any level from being a small time pirate to the ruler of a large empire. You can fight, trade, explore, build factories, and amass a fleet to form your own faction and conquer others’. The universe is dynamic and fully simulated, NPC ships live their own lives, factions are able to conquer territories and conduct diplomacy while their economy influences their military production and capacity. Missions are generated based on what’s actually going on in the galaxy, instead of what is usually the other way around.
Unending Galaxy is available for Windows PC. It’s a 100% single-player, offline game with no DRM or advertisement.
Mobile Chess (for Java ME) and Flash Chess (for Web) with Strong Chess AI.
UPDATE: This software seems outdated. Take a look here for an alternative… Link and here is the Gamemaker full list
Open RPG Maker is a free and open source 2D RPG creation utility, similar to the popular RPG Maker series. Open RPG Maker is mostly based on RPG Maker 2003, but with some added features, and more advanced usability. This tool will allow users to create 2D RPG games similar to the original Final Fantasy games, such as FF5 and FF6. Though it will also support the creation of games following a Zelda like playability. Unlike the RPG Maker series, Open RPG Maker will have the ability to play more than just midi and wav music files. Open RPG Maker will also be using 32×32 tiles of up to 24bpp, instead of the 16×16 8bpp limit in RPG Maker 2003. Also, Open RPG Maker will support more than just PNG graphics formats.