This very question (If you were going to open up a shop, what would you sell?) was the subject for Table Topics at a recent Toastmasters meeting. I've never been interested in going into business for myself. But if my husband had the money to open a shop, I know what we'd be doing.
My husband would love to have a gaming store. All kinds of stuff for role-playing games (Dungeons and Dragons, Champions, and lots of others that I've never heard of because I'm not into gaming the way he is). That means books, figurines, dice, paper with squares or hexagons to map out scenarios on, etc.
And there would have to be room to actually run games in the store, which would mean also selling snacks to eat while gaming. And other kinds of games, because people who like gaming probably playing other games, such as board games, card games, and of course computer games.
Since a lot of that stuff – especially the books and games – can be purchased online, the store would have to compete (with online stores) largely on its ability to do what the online stores can't – bringing together people of similar interests. People can have fun playing online games with players they've never met, but there's something special about getting together in the same room, sharing the fun of what my husband calls "community story-telling."
Since I'm not the gaming enthusiast he is, my role would probably be in support – taking care of the business side of things (I do have an MBA) and the computer systems, keeping things organized, and maybe having a chance to do some creative, arts & crafts kinds of stuff with displays for different kinds of games.