Everything that's fun should have its own .fun domain name. Probably the most versatile extension out there. If you offer child animation or clown courses, then you will want to promote yourself via a .fun domain name. But also for websites offering games, puzzles, jokes of the day, cartoons or funny videos, a .fun domain name will certainly attract attention. In the serious business-world, a .fun domain will find its use for team building exercises, family events, year-end gifts etc.
A .fun domain name can be used for almost anything!
Disclaimer: using a .fun extension for the memorial site of your late mother in law might harm you marriage.