This one came to mind as soon as I read the word shopkeeper. Moneybags did not own a shop, he didn't sell too many goods or services but he held one trait that every shopkeeper should have: A love of money!
Moneybags followed Spyro the Dragon around like a hawk, finding inaccessible areas. After he learned to unlock them, he waited to charge our hero for access. His fees became more and more outrageous as the levels progressed.
Even with his world being on the verge of destruction, he still found a way to sate his love of money. He even sported a monocle and fancy suit, most likely obtained through his extensive extortion racket.
Moneybags served not only as a means to get rid of cold hard gems, but also became a character with a semi-fleshed-out profile. He wasn't a fighter, but he was against the bad guys. In a way, he served as a proving ground for the hero. He was essentially the force pushing Spyro to explore and collect more, expanding the limits of our scaly hero.
Psychoanalysis aside, the bear loved money. He was greedy and only thought of himself. But he did make me go back and collect every gem in the individual levels, which made me want to 100% them. He was a proving ground to me, as I wanted to have the cash to pay him the instant he asked. It was like pushing him aside and saying "Let me through!" in a big booming voice. So satisfying.
Image Source: Spyro Forums