github-monospace.user.js

// ==UserScript==
// @name         GitHub monospace
// @namespace    http://kkaefer.com
// @match        https://github.com/*
// @author       Konstantin Käfer
// @description  Changes GitHub's table listing to monospace
// ==/UserScript==

(function() {
  var style = document.createElement('style');
  style.innerText = [
    '.tree-browser { font-family: Menlo, "Bitstream Vera Sans Mono", Monaco, monospace; }'
  ].join('\n');
  document.head.appendChild(style);
})();