By Ann Saphir and Tom Polansek

CHICAGO (Reuters) - Oil major ConocoPhillips, billionaire investor Carl Icahn, Coca Cola and giant energy trader Mercuria are among a crop of previously unnamed, high-profile former clients of bankrupt futures brokerage MF Global, an examination of claims filed in the case shows. Fifty of MF Global's bigger former customers -- including large hedge funds, multinational powerhouses, and other major traders -- had about $1.2 billion lodged with MF Global when it collapsed, according to a Reuters analysis of about 10,000 of the nearly 28,000 claims in the case.

Together these top 50 accounted for more than a fifth of the broker's total customer funds. The claims shed new light on what was once one of the world's most active commodity brokerages, showing it attracted big-ticket clients along with the farmers, ranchers and retail investors who have raised the loudest cry over its collapse. Five directors of exchange operator CME Group have also filed claims, an indication of how the company's bankruptcy caught even well-informed investors by surprise. "We had nothing against MF Global. We thought they were a good firm," said Icahn, who has a claim but is not among the former clients baying for blood. Like most traders with commodity accounts at MF Global, Icahn has gotten about 72 percent of his money back. Even if he never sees the rest of those funds, Icahn said he will have made $15 million or so during the year the account was open. His account at MF Global backed a single options trader, a bit player in the scheme of Icahn's $9 billion fund. It held $85 million on the broker's final day of business, October 31.

Marathon Petroleum Corp, Nestle SA, General Mills Inc, Anheuser-Busch Inbev, energy giant Tesoro Corp and Spam-maker Hormel Foods Corp are among the companies still waiting on the return of at least $333 million, based on the analysis, which may not capture all of MF Global's biggest former customers.

A spokesman for the trustee declined to identify the top MF Global claims, citing privacy concerns.

ALLURE

Investors were attracted to MF Global, run by former Goldman Sachs CEO Jon Corzine, for its relatively low trading fees, name recognition and specialization in commodities trading.

Nestle used its accounts in futures transactions for a mix of commodities, said Prashant Kulkarni, a risk management lead for the company. The chocolate maker has received back about 72 percent of the nearly $9.2 million in its accounts, he said. Options trader Billy Hunt moved his money to MF Global after Goldman Sachs, his broker of many years, told him it would no longer back individual traders like him. He selected MF Global because he was a former client of its predecessor, Refco.

Hunt kept a large balance - $26 million when MF Global went under - in his accounts to back his specialized, high-margin trades.

He shifted money to MF Global just two months before it collapsed and has yet to recover about $7.9 million.

Other big traders were linked to MF Global because they worked with other brokerages that cleared trades through the firm.

Daniel Bowman, a cattle trader in Chicago, saw his accounts transferred to MF Global when it bought his longtime brokerage Dowd Wescott. He had his life savings at MF Global, including a $5 mln Treasury bill and $2.5 million in cash, he said. He is still waiting for $1.5 million back.

"I'm at retirement age and he's got all my money," said Bowman, 74, referring to Corzine.

FLEXING MUSCLES It was hard for even big traders to escape MF Global in the days before it imploded. Many became nervous after the broker disclosed it had made risky bets on European sovereign debt. Magic Capital, a $25 million hedge fund that did its futures trading and kept virtually all its capital at MF Global, decided three days before the bankruptcy to pull its money out, said Jennifer Yu, a back-office manager at the Rockville, Maryland-based firm. But the transfer request did not go through in time.

Now Magic is 28 percent smaller, due to the amount the bankruptcy trustee has held back. Segregated accounts were supposed to keep customer funds safe, even if the broker failed. MF Global's European exposure also spooked Highridge Futures Fund, a hedge fund that had $50 million in accounts. Highridge general partner Michael Recine said he also tried to empty the accounts three days before MF Global collapsed but "for some reason my bank couldn't handle the whole transfer." DRW Holdings, one of Chicago's biggest trading firms, is one firm that closed its accounts early enough. It had about $5 million at MF Global when the broker disclosed on October 25 that it had put a $6.3 billion bet on European sovereign debt. DRW immediately withdrew all but about $9,500 from its MF Global account. DRW chief Don Wilson says such debacles could be prevented through more transparency about where and how brokers invest their customers' money. "If we had been aware of the risks they were taking ... we would have pulled our money much sooner," he said.

Other firms pulled money from MF Global before the bankruptcy, as well.

MF Global had $8.8 billion in customer funds at the end of July and only $7.2 billion by the end of August, Commodity Futures Trading Commission data shows. By its collapse, the amount was $5.5 billion, according to CME Group. Stricter rules -- including holding CEOs accountable for safekeeping of segregated funds -- and stricter punishments, including potential criminal sanctions, are among proposals under discussion by industry groups including the National Futures Association and the Commodity Customers Coalition, which represents former MF Global clients.

SURVIVORS Industry insiders say it is not unexpected that MF Global -- which was among the top 10 U.S. futures brokers -- would have large hedgers as clients. Such companies were generally equipped to handle the collapse better than smaller investors. To these titans, the money still tied up at the failed brokerage is fairly inconsequential. Unlike the smaller players who made up the majority of MF Global's 30,000 customers, most of the big firms had accounts at several brokers and giant trading desks. ConocoPhillips, the world's No. 5 refiner which earned $3.4 billion in the fourth quarter, had accounts valued at $310 million with MF Global on October 31, including $195 million in letters of credit to guarantee its trades. ConocoPhillips spokesman Aftab Ahmed said the bankruptcy "did not impact any of our underlying operations." He declined to say how much of that balance had been returned to ConocoPhillips. Global trading company ITOCHU International also said the impact on business operations was minimal. Yet, the collapse "changed our view that our accounts are fully secured," in-house counsel Keisuke Nomura said. "We need to pay more attention to the credibility of the companies like MF Global," he said.

THREAT TO CME? Most large investors have kept their exposure to MF Global under wraps, while farmers, ranchers and individual traders have sounded off to the media, the trustee and Congress over the $1.6 billion in customer money still missing. Yet these larger customers are critical to the futures industry, and to exchanges like CME Group Inc and IntercontinentalExchange Inc, which could suffer if big-name investors take their business off the exchanges to over-the-counter deals.

In contrast, farmers and ranchers have few options besides the regulated markets to hedge their products. CME and ICE have been clearing more over-the-counter contracts, but their main futures business generates higher margins. "What the exchanges care about is volume," said Craig Pirrong, a professor at University of Houston. "If one or two of these big guys move to the over-the-counter markets or cuts down trading substantially, it could be a big deal." At a recent roundtable convened by the CFTC, players such as bond fund giant Pimco, mutual fund company Vanguard and the California Public Employees' Retirement System made clear that their main concern was that their money would be as protected in the futures markets as it is in the over-the-counter markets. CME has been working to hasten the return of, and protect, all customer funds, a spokeswoman said. Former MF Global clients Coca Cola Co, Hormel, General Mills , Anheuser Busch, Tesoro and Marathon Petroleum declined to comment for this story or did not return calls for comment.

CME DIRECTORS One measure of how MF Global's bankruptcy caught even savvy investors by surprise is the five CME Group directors who filed claims. Two of them -- former vice chairman Charles Carey and director Joseph Niciforo -- are suing the broker. Jack Sandner, a former CME chairman, and director Robert Corvino also had small claims, while director David Wescott had $2.1 million in an MF Global account. All declined to comment or did not respond to requests for comment. Glenn Pankau, whose brother Ron is on the CME board, had banked some $650,000 at his MF Global account, much more than the $50,000 he needed to secure his personal trades. "I was always told it was the safest place my money could be," Pankau said. On the Friday before the bankruptcy, Glenn Pankau had a conversation with Wescott, a CME director and MF Global officer. Wescott told Pankau he should take his money out of MF Global if he was uncomfortable. Pankau tried, but the check bounced. To date Pankau has retrieved only 66 percent of his money from MF Global. Wescott has received none. Now, Pankau keeps only enough money at his new broker to back his trades. "I am not going to be victimized again," he said.

(Reporting by Ann Saphir and Tom Polansek; Editing by David Gregorio)