Sling bags are the current trend mainly for their sizes and carrying capacities. Basically, you don't need to be overweighed with a big backpack any longer, not when you can easily throw a sling bag over your shoulder and go about your normal duties without any troubles. A good crossbody bag can give you very quick access to a lot of basic essentials on the move. Now that's an easy way to beat pick pocketers isn't it?
They are also lightweight, adjustable, flexible, and allow you to freely move with your small things well organized. This can be worn as shoulder bag too.