Similar to a brick and mortar convenience store, but online and all prices in XMR? I could see such a store selling things like coffee filters, bar soap, tissues, feminine products, etc. However i dont know that it could work with being online since you could just go to the local wallgreens/cvs. The only way i could see it working is if a person was Monero only and totally refused to use fiat. As of now you can buy Gourmet coffee, meat bars, a plane ticket, etc with xmr but if you want a coffee filter and a box of granola bars you have to deal with fiat conversion and a gift card.

Edit: Not to say plain tickets aren’t important because they are, but how often are you buying a plain ticket compared to coffee filters and tissues