My favorite shop dog was a Golden at the small mom/pop pet supply store. Every time someone went in, he'd go stand by the open bin cookies and bark once. He was allowed to have a cookie if a visitor wanted to give it to him, and he'd figured out how to ask for it.
Eventually, the owner had to tell people to only give him one of the tiny kibble-sized treats.
I was always impressed that he'd ask for the cookie and not just dive nose first into the bin, like Roscoe would!
I also love shop cats. There's an absolutely enormous Maine Coonish cat at a book store near my aunt's house, and he sleeps on the checkout counter. He walks over for headbutts and skritches when you check out.