The Amiga is probably the most sensibly organized (C, Devs, L, Libs, S, etc) OS ever. In hindsight, it's a shame a few others weren't standardized early on like:
Vault: a standard place to put keyfiles and evolved config files like Dopus's. Easy to back-up.
Sounds: standard system sounds
Logs: installation log files
Wouldn't a vault be a bad place to keep a key, especially if it was the key to the vault? Still, it's a cool name if only for the fact it reminds me of Fallout...