My favorite:

Let's look at a typical novice's session with the mighty ed:

  golem> ed

  ?
  help
  ?
  ?
  ?
  quit
  ?
  exit
  ?
  bye
  ?
  hello? 
  ?
  eat flaming death
  ?
  ^C
  ?
  ^C
  ?
  ^D
  ?

  ---
  Note the consistent user interface and error reportage.  Ed is
  generous enough to flag errors, yet prudent enough not to overwhelm
  the novice with verbosity.

That's one of my very favourite pieces of tech-related comedy. I still laugh every time.