It’s all the craze at the moment. Your very own personalized crypto wallet address. Think crypto. Think wallet address. Think human readable name. You can also use it as a website domain. They’re fairly inexpensive if the name is right and you only pay once. And it’s a NFT!
I picked up a couple variations for $20 each. You can use the following extensions:
I looked at these about 3 months ago and had an idea to buy a few. However, we bought 2 private UK car number plates a decade ago, so before I decided to buy any unstoppable domains, I did a “back test” and filled out an internet form to see what value my private plate had. I bought it for £500, now it MAY be worth £600. That is less than 1% per year capital gain. And then if I sold it, I would then have to remember a stupid number like aaa nn bbb where a and b are letters and n is a number starting designating the year of registration that only the British public sector, in their infinite wisdom, could devise.
I decided against buying “speculative” unstoppables because anything recognizable is a few hundred dollars. I did note, however, that some for $20 or $40 would be great value.
Two things have stopped me. First, I don’t know where I would go for a domain name host. Second, having a .crypto address may be a great advertisement for the thieves to do some social engineering thinking you had a Trezor in the safe at home with a million dollars of ETH stored on it, so they kidnap your children and demand a ransom. 
That’s thoughtful thinking there. i don’t look at the domains as an asset I’m looking to offload in the future. At least not the ones I would use personally to receive crypto. Now, having seen first hand that the right domain can be sold for 100s of thousands and every-now-and-then millions, buying and selling crypto domains could turn into a lucrative business. However, Unstoppable has already priced in that potential future sale. so becoming a broker and amassing 10s or 100s of these will cost you a pretty penny. Some of the more basic and general term domains are several thousand dollars already.
I bought mine for the “that’s cool” factor. And the no-renewal costs was a bonus.