Jay-Z
The rapper Jay-Z, 42, started the year off strong — with the January birth of Blue Ivy Carter, his daughter with wife Beyoncé Knowles — and never lost momentum, whether he was starting his own musical festival (Philadelphia's Made in America fest), performing eight sold-out shows to mark the opening of his hometown Brooklyn's new Barclays Center arena (where the Nets, the basketball team of which he's a part owner, also play) or (reportedly) buying a generator to keep the lights on for his neighbors affected by Hurricane Sandy. But in 2012, Hova also made his mark on a larger scale: as one of the highest-profile surrogates for President Obama's re-election campaign — he even remixed his hit single to include the words "I got 99 problems, but Mitt ain't one" at a Columbus, Ohio, rally — he changed what it could mean for celebrities and politicians to work together.