How about that editor (or rater, originally a set of
macros for an
editor) that implements a LISP interpreter, which can be an e-mail
client, news reader, ELIZA, ftp client, play tetris, be an IDE, etc,
etc...
Somewhat older that Netscape. Caused more flamewars, too. (Hope
I'm
not starting one here!!!)
Oooh, yeah...
That block of code would be a great OS if it had a decent text
editor.