1. If you choose a generic top-level domain, you may be considered as spam:
Although .com are becoming common and sometimes boring, everyone on the web considered them normal for websites and online stores. Spammers sometimes use irregular TLDs as they can purchase a lot of them for a cheap price. If you are planning to use one, you will have to work hard to promote yourself as a secure and reliable brand.
2. Be unique and memorable:
Another issue with using an unusual domain extension is that your customers might not understand it or remember it. When choosing TLD, make sure to sound natural. Keep the name as short as possible. Nobody wants to remember a long and complicated name.
3. Have your top-level domain fit your Shopify store:
If you sold coffee mugs, we suppose you prefer your store to be called www.drink.coffee as opposed to www.drink.party.
Come up with a domain that stands out!