2. Justin Bieber: 21 Under 21 (2013)

Last Year's Rank: 1

Birthdate: March 1, 1994 (Age 19)

Why He's Hot: 2013 hasn't been the best year when it comes to good press for Justin Bieber. But even lending his car to a bonehead and being caught urinating into a janitor's mop bucket and yelling "F--k Bill Clinton" at a picture of that U.S. president couldn’t squelch the Canadian’s fame. At the top of 2013 his "Believe Acoustic" ruled the Billboard 200 -- giving Biebs his fifth No. 1. And Justin has made plenty of waves since — whether he’s assisting will.i.am to a No. 17 spot on the Hot 100 with “#thatPower,” rapping shirtless in hardly known singer Maejor Ali’s video or escorting boxer Floyd Mayweather to the ring for a championship bout. His “Believe” tour is currently selling out huge venues all over the world. Not to mention he’s the king of Twitter, besting all with nearly 45 million followers.