Quick Mobile Detection. Yes I know, it's probably better to do feature detection rather than UA sniff, but sometimes for smaller projects you just need to know whether or not you're on a mobile device without having to load in a larger library.

quick-mobile-detection.js

var isMobile = {
    Android: function() {
        return navigator.userAgent.match(/Android/i);
    },
    BlackBerry: function() {
        return navigator.userAgent.match(/BlackBerry/i);
    },
    iOS: function() {
        return navigator.userAgent.match(/iPhone|iPad|iPod/i);
    },
    Opera: function() {
        return navigator.userAgent.match(/Opera Mini/i);
    },
    Windows: function() {
        return navigator.userAgent.match(/IEMobile/i);
    },
    any: function() {
        return (isMobile.Android() || isMobile.BlackBerry() || isMobile.iOS() || isMobile.Opera() || isMobile.Windows());
    }
};

// Quick iOS Test
if( isMobile.iOS() ) { alert('You\'re on an iOS device.'); }