Corona for Cinema 4d_free for commercial use
Corona render is a photo realistic render widely used in architecture and product visualization. It is basically released for 3ds max. But they are hardly working on Cinema 4d plugin. You can download a free commercial version(alpha ver) now. It will be expired once the final version is announced.You can use it on commercial projects also. But honestly speaking it is very good render even at the alpha stage.
It is truly based on CPU engine and is far better than C4d native render in photorealism and quality.
Download the render here
Here is a little tutorial for getting familiar with corona for cinema 4d