There are a number of “have-to” lists in Paris, places where people just have to go while they’re here. Often people have limited time, and I hear ya, so I might suggest the departments stores on the Boulevard Haussman, Printempts and Galeries Lafayette (although even since Printemps started charging €1,5 to use the restrooms, I’m inclined to go to the Galeries Lafayette, just on principle.) Some of the well-known chocolatiers and pastry shops have kiosks in those stores, so you can hit the “big names” in one fell swoop. If that’s your thing.
For those wishing to shop on a smaller scale, there’s La Graineterie du Marché at the excellent Marché d’Aligre. It’s the only outdoor market in Paris that’s open every day, except Monday, and in the center of the market, you’ll find José Ferré tending to his lovely, old-fashioned dry goods shop.