John McEnroe
Day job: Retired tennis player, gallerist
Collects: Contemporary American art
Collection includes: Alice Neel, Eric Fishl, Ed Ruscha, Jean-Michel Basquiat, Neil Jenney
Fun fact: Poor guy lost $2 million in 2009 in a major scam by former art dealer Lawrence Salander, who sold the same painting to McEnroe and another collector, though neither ever saw the real thing. Salander is now spending 6-18 years in prison for it; McEnroe, on the other hand, owns a gallery in SoHo.