Zmacs
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One of the many variants of the EMACS text editor, Zmacs ran on the Lisp Machine (I believe it was only called Zmacs on Symbolics boxen -- if you know more, please edit this page).
A distinctive feature of Zmacs, which can also be found in Hemlock and LispWorks, is that commands look like "M-x Compile Buffer" instead of "M-x compile-buffer", an in GNU Emacs.