Particularly food stores, but also selling books, pets, clothing and shoes, even antique types selling "clutter". I'd like them to be interactive, with the shopping part to be done in a similar way to selecting a book from a bookshelf - only with multiple selections possible. Also with food to be available in two grades, normal and gourmet, so foodies have a little more control over quality at a price. And with your sim to be able to chat with other shoppers and the cashier, who could have a specific "checkout" option when you're done yakking. It would also provide more jobs for Townies or part-time workers, and possible business ownership opportunities.