Today I was bumming around in /usr/share/emacs/23.0.91/etc/ and I found the HELLO file. That directory is full of such gems, but I was wondering if there are other, more obscure, easter eggs in emacs that you all might know about. From a terminal window run emacs like so:
emacs --no-splash -f view-hello-file
This starts emacs and opens the HELLO file.