Football teams, islands, mansions and yachts are just a few of the things popular with the world's richest, but it seems some billionaires have more unusual hobbies, and are willing to part with serious cash to indulge their interests.
Hedge fund manager and general partner of WG Trading, Paul Greenwood made headlines in 2010 not just because he was charged with conspiring to defraud investors of some $554 million. Greenwood also sold his teddy bear collection worth $1.75 million at auction, reportedly to help pay his legal fees.
Here we take a look at five other billionaires collectors, compiled by high-end collectibles firm Paul Fraser Collectibles.
Bill Koch – worth $4 billion
Collects: Wild West and maritime memorabilia
Charles and David Koch of Koch Industries are both said to have $41.5 billion in wealth each, making them the 6th richest men in the world according to Forbes. While younger brother Bill has just a fraction of their wealth, he seems to spend a good chunk of it on memorabilia. Koch's collection includes antique maritime memorabilia such as nautical instruments and model ships after his boat won America's Cup in 1992. He also bought the only authenticated photograph of U.S. outlaw Billy the Kid for $2.1 million in 2011 to go with his Jesse James gun and General Custer flag that form part of his million piece collection of Wild West memorabilia. Koch has also built a Wild West style town in Colorado called Bear Ranch.
Bill Gates – worth $80 billion
Collects: Da Vinci, cars and U.S. art
Microsoft co-founder Gates is the second richest man in the world, known for the vast amounts he gives away to charity, but he is also keen art and car collector. In 1994 he bought the Codex Leicester of scientific writings by Leonardo Da Vinci for $30.8 million. He also owns a Porsche 930 Turbo, a Jaguar XJ6 and a Ferrari 348. He paid $36 million for Winslow Homer's Lost on the Grand Banks in 1998, a record price for an American painting at the time.
Carlos Slim – worth $81.5 billion
Carlos Slim, listed as the world's richest man by Forbes, is said to have a 66,000-piece collection of art according to Paul Fraser, including works by Da Vinci, Picasso and Renoir. Slim is thought to own the second biggest collection of Rodin sculptures outside France, with much of his collection on display in his free museum in Mexico City. There you can also see his collection of rare coins, historical documents and religious relics.
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Bruce Halle – worth $4.9 billion
Collects: Tire posters
Halle, founder of tire chain Discount Tires which employs more than 15,000 people, is an avid collector of vintage tire posters. He is said to have a collection of 400 lithographs from the last 100 years. He told Forbes he is the owner of a number of Toulouse-Lautrec posters as well as some early Michelin posters.
Truett Cathy – worth $6.3 billion
Collects: Classic cars
Founder of fast food chain, Chick-fil-A, Cathy is now aged 93 and owns around 70 classic cars including the Batmobile from 1992 movie Batman Returns and three limos.
Cathy, who has said in the past that he has no interest in new cars, also counts a 1916 Model T Ford and a 1981 Delorean, made famous by the "Back to the Future" movies, as part of his collection.