The Ducks Unlimited Store is a decent example of a magento site that was expanded upon using magento’s good code model to fill the needs of a higher end client.
The store sells Ducks Unlimited Apparel including Men’s Camo Hoodies, dog embroidered clothing, and many other items.
They have an ERP that needs to talk nice with their store software, so the flexibility of magento was used to generate reports in a format that would easily integrate with their ERP.
I didn’t do this application, I inherited it, but I must say it is nice to see how magento can be stretched while still leveraging the core functionality it provides.