Punycode is used for representing Unicode with ASCII. Some uses for it are:
Emoji domains: ✓✉.tld (xn--4bit.tld)
ASCII-like domains: ౦೦օ๐໐᠐〇.tld (xn--zbb536a8kx0cks675b9r3b.tld)
Invisible domains using U+2008: ⠀⠀⠀⠀.ga (xn--6iiaaa.ga)