One I read in a HN comment a while back was to find available domain names and come up with ideas for them.

When I saw that my first name was available with the .chat TLD I knew it should be one of two things: a redirect to my calendly, or an immediately-available IM session with me when I'm available (just for fun).

Built the latter this morning to have an excuse to buy the domain! You can see it at Alexander.chat.