For smokables: Bud, budder, hash, oil in all different levels of quality. Should be organized by Sativas, Indicas, hybrids in addition to being separated by potency and type of high (head, body). Should also carry pre-rolled joints & blunts.
For edibles: Baked goods, candy, sugar-free options, teas, etc. Should have MANY options. Also should have the option to buy canna butter and oil for those that want to do their own cooking at home.
For plants: Large selection of seeds, clones, and mother plants. Should also carry hps/mh lighting setups amongst others like florescents and LED, supplies for both hydro growing and soil.
For smokeware: Should carry different styles of vaporizers (forced air, whip style), high quality american made glassware, cheap pipes. You want something for everyone from inexpensive to bubblers that cost $6,000 or more. Having an in-house glass blower would be a huge plus.
Books: Various books about cannabis history, usage, gardening, etc.