It’s no secret that U.S. stocks had a great year in 2013. The S&P 500 gained more than 22% through mid-December, building on its 13% rise in 2012. Fortune 500 companies were no exception, with 86% enjoying share price increases, compared with less than 80% last year. And while two solid years in a row isn’t exactly a comeback story, several of 2013’s surprise best performers, who posted dazzlingly high returns after being down-and-out a year ago are. Indeed, the Fortune 500’s top 20 performing stocks doubled their share prices. And the big winners? Fannie Mae and Freddie Mac, penny stocks a year ago, returned nearly 1000% as they repaid their government bailouts. The rest of the top 10 run the gamut from health care to casinos. Click through the countdown of the best Fortune 500 stocks of 2013, based on their closing prices Dec. 6. –Jen Wieczner