It turns out that some kind hearted people already set up wildcard domains for you already. You can use any domain below and/or any subdomain of these and they currently resolve to 127.0.0.1 but could switch at any time to resolve somewhere else. Here's the list of ones I know about. Let me know if there are more!
localhost- It will always works. Do you know why? I hope so.[*.]fuf.me- Managed by @fidian; it will always point to localhost for IPv4 and IPv6[*.]fbi.com- 👏 👏 👏 👏 👏[*.]localtest.me[*.]127-0-0-1.org.uk[*.]vcap.me