Billionaire investors took major risks in 2014. Stock plays in the health care sector seem to have paid off the most. Glenview Capital Management's Larry Robbins made a bet early on that Obamacare would have big implications for the health care industry in the United States. His instincts turned him into one of the top-performing hedge fund managers in recent years, and by the looks of it, other Wall Street magnates are following his lead. Plus, investor Seth Klarman made about $1 billion from putting his money into Idenix Pharmaceuticals, which was acquired by Merck & Co (MRK), sending shares and Klarman's net worth through the roof. But not all of the billionaire bets paid off. Oil prices have hit a new five-year low and some analysts say crude could dip as low as $40 per barrel next year. Falling prices didn't bode well for billionaires like Carl Icahn who picked oil companies like Transocean (RIG), Chesapeake Energy (CHK) and Talisman Energy (TLM), which have tumbled in recent months.