As I was searching to find what can I print for my car, I found Mark and his company. It is an excellent example how 3d printing can help a small company to make custom products. They use 3d printing to make custom car audio speaker boxes, pods and attachments that look vary cool.
They may run out of business when 3d printing spreads and Maker / DIY culture becomes mainstream ;-) Probably not, as they certainly have creative spirit which will enable them to thrive on the market.
3D printed A-pillar speaker pod:
3D printed car subwoofer box:
Here is the company page: