Industry News Bruno Mars' 'Grenade' tops chart, Katy Perry's 'Firework' second 01/27/2011 Bruno Mars's "Grenade" is No.1 on the U.S. record chart, Billboard.com reported Thursday. Read More RELATED NEWS Jimmy Fallon's 'The Tonight Show' dropping to only four nights a weekAshley Tisdale announces birth of her second childSelena Gomez is a billionaire TAGS: Britney Spears Katy Perry P!nk Bruno Mars T-Pain Rihanna Ludacris Wiz Khalifa Pitbull Enrique Iglesias
