For when you really want your shit on top.

fuckYouIWantMyShitOnTop.js

var fuckYouIWantMyShitOnTop = function (idOfElementYouWantOnTop) {
  var all = document.getElementsByTagName("*"),
      maxZIndex = 9007199254740992, // https://gist.github.com/jsatk/7921133#comment-968150
      i, highestZIndex, currentZIndex, currentEl;

  for (i = all.length - 1; i >= 0; i--) {
    currentEl = all[i];
    currentZIndex = Number(currentEl.style.zIndex);

    if (isNaN(currentZIndex)) continue;

    highestZIndex = isNaN(highestZIndex) || currentZIndex > highestZIndex ? currentZIndex : highestZIndex;
    currentEl.style.zIndex = currentZIndex === maxZIndex ? currentZIndex - 1 : currentZIndex;
  }

  document.getElementById(idOfElementYouWantOnTop).style.zIndex = highestZIndex + 1;
};

Page 29 of the ECMAScript (under ECMA Section 8.5 - Numbers) spec states:

Note that all the positive and negative integers whose magnitude is no greater than 2⁵³ are representable in the Number type (indeed, the integer 0 has two representations, +0 and −0).

So,

var fuckYouIWantMyShitOnTop = function (yourElementYouWantOnTop) {
  yourElementYouWantOnTop.style.zIndex = 9007199254740992;
}

OK now that's just rude.

Another way maybe to do it would be to wrap the entire contents of the body in a <div> with position: relative; z-index: 1; and like overflow: auto; then insert your thing AFTER that div with also some positioning other than static and a z-index: 2; - That way everything else is stuck in that new context and your stuff is in a new, higher context. I think that should work.

You might want to lower the zindex of everything else that is at 9007199254740992.

@joelmccracken @msepcot Done :)

@chriscoyier that's brilliant and terrifying. This entire thing is terrifying and was created as a joke. The only real use case I can see for this is if you're on a giant project and some element keeps getting covered up by other non-careful coders who abuse z-index you could invoke this script with the ID if the el you want on top somewhere ;)