Bennugd

Bennugd  is a high level open source game development suite which focuses on modularity and portability, making it a perfect choice for cross-platform game development.

Bennugd Official Page

Although officialy it is only supported on Windows, Linux, Mac  and GP2X Wiz (on the right), Bennu can run on multiple other platforms, including *BSD, MacOSX and other consoles such as the Wii, Playstation2, PSP, Dreamcast, Raspberry,  Dingoo A320, GP2X, or the classic Xbox.
This makes it really fun to code in Bennu: the game can be played on you computer AND your console!

Bennu -which was born as a Fenix fork- is actively mantained and makes it easy for both beginners and experienced users to create their own games.

The latest will find it particularly interesting that Bennu allows the use of third-party extensions that extend Bennu to allow such things as: networking, advanced output graphics manipulations, mpeg playback, complex text rendering, XML parsing...

In fact, most of the Bennu code runs as extensions to the main interpreter, allowing you to use only those you need (thus optimizing resource usage) or to completely replace them.

For example, you can choose to replace the provided 2D software renderer with an OpenGL 3D renderer  that also provides an advanced physics engine.