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.
Simple to use, many features, lots of good games, great GUI... The best part is that you get a good program for free, also you don't need other programs to make models and textures because everything is already in Blender. Try it now!