Via Toledo 214
This is a chocolate shop, quite famous in Naples. There are a wide selection, from plain chocolate to nut-filled to truffles with fillings. They also sell bars of chocolate, the best of which is the dark bitter chocolate. Also good are the coffee beans coated with chocolate. Very bitter inside but a delicious combination.
As with any pasticcerie, you get the beautiful paper wrapped with ribbon. Italians take such pride in what they sell. Even if you buy a couple of sweets, they will make sure it's wrapped nicely.
There are a few branches throughout Naples, but I think the one on Via Toledo is the main shop.