10. Chief Keef: 21 Under 21 (2014)
Birthdate: Aug. 15, 1995 (Age: 19)
Last Year's Rank: 12
Why He's Hot: After Kanye West remixed his single "I Don't Like" in 2012, many wondered if Chief Keef was a one-hit wonder. But the Chicago rapper (real name Keith Cozart) has proved his doubters wrong. Two years later, Keef continues to lead the thriving drill movement. Since first making his mark, he's released hits such as "Love Sosa" and "Emojis," and is prepping to release his upcoming second album, Bang 3, which features a collaboration with 'Ye titled "Nobody." Meanwhile, the once-notorious Keef seems to have put a tap on his run-ins with the law; he recently served 90-days in rehab and celebrated his release by learning how to surf while in Orange County, Calif.
Billboard's 2014 21 Under 21 List