I was asked to help build and design a paintball gun from some flat sketches and material swatches, and below is the result of the project. The rendering seen below was very labor and processor intensive. I paint in Photoshop my own custom 32 bit HDR emitters to light my products and scenes. The results are quite fine.
Below is the ambient lighting pass, which was one of probably tweleve or so total lighting passes that I used. Everything was then composed in Photoshop, including the z-depth pass as also seen below.