Toshihiro Kushizaki has released his Pixel Art Shader for Blender. The Pixel Art Shader will render out models in the old school pixel shader art style.
All you need is a Blender polygon model and a designated color pallet to use (that will limit the number of colors rendered), and a configuration script to render out any model in a Pixel Art Style.
The site is in Japanese, so it is a little cryptic to get around if you don’t speak the language (even with translation), but it does look like the Pixel Art Shader for Blender does an amazing job from the images shown online. There is also online documentation provided, as well as a download. Check out the Pixel Art Shader for Blender here.