news.*
Usenet's hierarchy about Usenet itself — groups for new users, administrators, newsgroup proposals and the collected FAQs of everything.
Where other hierarchies were about computers or hobbies, news.* was about the machinery. news.announce.newusers regularly posted introductory texts on how to behave, an early distributed form of netiquette. news.announce.newgroups carried proposals and votes for new groups in the Big 8, and news.groups was where people fought about them. news.admin.* was home turf for the people running servers, with news.admin.net-abuse as the front line against spam.
The moderated group news.answers gathered periodically posted FAQs from all over Usenet, and they were archived on, among other places, rtfm.mit.edu — a hostname that told you exactly what you were expected to do before asking.