"On your keyboard, idiot!" - To quote SE user Macha on the <kbd> tag (http://meta.stackoverflow.com/posts/comments/3247): 'Now all they need is an onclick handler to make them look like you are pressing them. Then an alert box pops up and says "On your keyboard, idiot!".' Well, here you go.

kbd.user.js

// ==UserScript==
// @name On your keyboard, idiot!
// @description For those who just keep clicking <kbd>s.
// @namespace michaelb958
// @author michaelb958
// @license MIT (http://opensource.org/licenses/MIT)
// @include *://*.stackexchange.com/*
// @include *://*.stackoverflow.com/*
// @include *://*.serverfault.com/*
// @include *://*.superuser.com/*
// @include *://*.stackapps.com/*
// @include *://*.askubuntu.com/*
// @include *://*.mathoverflow.net/*
// ==/UserScript==

function with_jQuery(f) {
  var s = document.createElement("script");
  s.type = "text/javascript";
  s.textContent = "(" + f.toString() + ")(jQuery)";
  s.setAttribute('data-with-jquery', '');
  document.head.appendChild(s);
};

with_jQuery(function($) {
  $('<style type="text/css">')
    .text('kbd:hover { border-style: outset; } kbd:active { border-style: inset; }')
    .appendTo(document.head);
  $(document).on('click', '*:not(a) > kbd:not(:has(a))', function() {
    alert("On your keyboard, idiot!");
  });
});