As 2014 rapidly approaches, Guitar World is taking a nostalgic look back at the most popular GuitarWorld.com stories, videos, lessons and features of 2013. Be sure to check out our other Year in Review stories here! Today, we're revisiting the 10 most popular "viral" videos to be shared on GuitarWorld.com. How did we determine what was the most popular? Let's just say it all came down to web traffic!