Just for fun — Add Konami Command (secret code) for your site.

Wrote something extremely stupid — a Konami secret code handler. You can try it on my site. http://www.jonycmusic.com/ (Up-Up-Down-Down-Left-Right-Left-Right-B-A)

Code source: http://jsfiddle.net/jonyc/8XSaS/4/

/*
*  
*  AUTHOR: Jonathan Cheung
*  KonamiCodeTrigger.js
*
*/
var KonamiCodeTrigger = (function() {
    // Saves the returned API
    var self;
    // Key History
    var keyCodeHistory = [];
    // All the triggers are stored in an Array;
    var __triggers = [];
    // Constants
    var Key = {
        UP: 38,
        DOWN: 40,
        LEFT: 37,
        RIGHT: 39,
        ESCAPE: 27,
        a: 97,
        b: 98,
        A: 65,
        B: 66
    };
// Here we store the winning Combinations..
    // The default is Up-Up-Down-Down-Left-Right-Left-Right-B-A / Up-Up-Down-Down-Left-Right-Left-Right-b-a
    var winningCombos = [
        String("" + Key.UP + Key.UP + Key.DOWN + Key.DOWN + Key.LEFT + Key.RIGHT + Key.LEFT + Key.RIGHT + Key.b + Key.a),
        String("" + Key.UP + Key.UP + Key.DOWN + Key.DOWN + Key.LEFT + Key.RIGHT + Key.LEFT + Key.RIGHT + Key.B + Key.A)
        ];
//Let's save the original
    var originalKeyPress;
    if (document && document.onkeypress) {
        originalKeyPress = document.onkeypress;
    }
document.onkeypress = function(evt) {
        var keyCode = Number(evt.keyCode);
        var charCode = Number(evt.charCode);
        
        //Process keyCode
        switch (keyCode) {
        case 0:
            break;
        case Key.ESCAPE:
            //Reset the history if ESC is pressed
            keyCodeHistory = [];
            window.scrollTo(0, 0);
            break;
        default:
            keyCodeHistory.push(Number(evt.keyCode));
            break;
        }
        //Process charCode
        switch (charCode) {
        case 0:
            break;
        default:
            keyCodeHistory.push(charCode);
            // Here's where we find out if the Konami code existed
            if (winningCombos.indexOf(keyCodeHistory.join("")) != -1) {
                __triggers.forEach(function(item, index) {
                    (typeof(item) == 'function') && item();
                });
            }
            break;
        }
        //Call our original keypress if it was there
        originalKeyPress && originalKeyPress(arguments);
    };
    
    return self={
        /*
         *  addTrigger()
         *  Adds a function to the callback stack.
         *  @callback {function} - The callback function you want to add
        */
        addTrigger: function(callback) {
            __triggers.push(callback);
        },
        /*
         *  removeTrigger()
         *  Removes a function from the callback stack.
         *  @callback {function} - The callback function you want to remove
        */
        removeTrigger: function(callback) {
            __triggers = __triggers.filter(function(item, index) {
                return item != callback;
            });
        },
        /*
         *   clearCombo()
         *   Clears the combo being used.
         *   @no prarameteres
         */
        clearCombo: function() {
            winningCombos = [];
        },
        /*
         *   addCombo()
         *   Adds a combo into the trigger. We can have multiple key combo to trigger the callback functions.
         *   @combo {string} - The string you want to use e.g. KonamiCodeTrigger.Key.A + KonamiCodeTrigger.Key.B
         */
        addCombo: function(combo) {
            winningCombos.push(String("" + combo));
        },
        /*
         *   removeCombo()
         *   Removes a combo.
         *   @combo {string} - The string you want to remove e.g. KonamiCodeTrigger.Key.A + KonamiCodeTrigger.Key.B
          */
        removeCombo: function(combo) {
            winningCombos = winningCombos.filter(function(item, index) {
                return item != String("" + combo);
            });
        },
        /*
         *   Key {}
         *   These are key constants.. You can add more to the Key costants above. Right now, only UP, DOWN, LEFT,RIGHT,A,B,a,b are in the constants as they are in the *original* Konami combo.
        */
        Key:Key
    }
})();
You can add more callback functions like this:
/* Put this guy in your onload */
KonamiCodeTrigger.addTrigger(function() {
    alert("BINGO! Now we do something interesting!");
});
And you can clear the original combo and add your own combo this way. (You need to assign the 'Key' object has the keyboard key mappings you want.)
//KonamiCodeTrigger.clearCombo();
KonamiCodeTrigger.addCombo("" + KonamiCodeTrigger.Key.A + KonamiCodeTrigger.Key.B);