The Blender Game Engine is a component of Blender, a free and open-source comprehensive 3D production suite, used for making real-time interactive content. The game engine was written from scratch in C++ as a mostly independent component, and includes support for features such as Python scripting and OpenAL 3D sound.
Maybe a not so high end engine but for some smaller scaled games its perfect, especialy that you dont have to use multiple programs for animation,modeling and the game itself! xD