Aufgeräumter

Array.prototype.unique = function() {
    var uniqueKeys  = {},
        uniqueArray = [],
        items = this.length
    
    while (items)
        uniqueKeys[this[--items]] = true
    
    for (var key in uniqueKeys)
        if (uniqueKeys.hasOwnProperty(key)) uniqueArray.push(key)
    
    return uniqueArray
}