If you impose structure on text you can do stuff like org-mode. If you allow networking, you can do emails like gnus. If you allow pictures and HTML parsing,

If you impose structure on text you can do stuff like org-mode. If you allow networking, you can do emails like gnus. If you allow pictures and HTML parsing, you can do a web browser like eww. I guess you don't have to add too much to get a new domain.