EmacsLisp

Emacs Lisp is the Lisp dialect used to write GNU Emacs and its universe of extraordinary add-ons, some of which are games. Emacs itself includes a number of games such as Tetris and Pong, and you can mess around with the source code if you're learning the basics of Lisp and want something you can use immediately with Emacs.

• Source code to Emacs included games and amusements
• Inform Z-Machine interpreter for interactive fiction

Basic knowledge of Emacs Lisp will greatly help in using and configuring GNU Emacs, so it is worth checking out even if you don't plan to play Tetris inside your editor.