On June 27, 1972, Bobby Hull stunned the World of Hockey by signing an unprecedented $2.5 million contract to play for the World Hockey Association's Winnipeg Jets. The 34-year-old left winger was parting ways with the Chicago Blackhawks where he spent the first 15 years of his career. Those 15 years included a second place finish in rookie of the year balloting, two MVP awards, five 50 goal seasons, 10 All Star appearances, and a Stanley Cup Championship. He had reached legendary status in the Windy City. However, the ole mighty dollar would lure him to the upstart WHA, which was in its first year of existence.
Hull gave the new league instant credibility, and the superstar had a lot left in the tank as he led the Jets to three Championships and took home two MVP awards. Hull returned the the ranks of the NHL when the WHA was absorbed by the league in 1979. He spent one more season on the ice splitting time between the Jets and the Hartford Whalers before hanging up the skates. He had spent 23 years on the ice, where he forged his Hall of Fame career.
You can view Hull's career numbers here: http://www.hockey-reference.com/players/h/hullbo01.html
This link is to a great piece done by ESPN as part of their Sportscentury series. It covers the story in greater detail, and also points out the fact that Hull opened the door for bigger contracts for hockey players.