1. Julius “Dr. J” Erving
As arguably the greatest player in the history of the franchise, without question, the signing of Julius “Dr. J.” Irving is the 76ers' greatest free agent acquisition. In the ABA, Erving became the face of the league winning three championships, four Most Valuable Player awards, he won the first Slam Dunk Contest, won three scoring titles with Virginia Squires and New York Nets (now the NBA's Brooklyn Nets).
Before the ABA-NBA merger, on October 20th, 1976, the 76ers brought Erving’s contract outright for $3 million in a deal that wound up being $6 million with Erving receiving the remaining money.
The investment paid off as Erving went on to 11 consecutive All-Star games, won an MVP Award, and was a part of one best NBA teams ever, the 1983 Sixers who won the championship. In 1993, he was inducted into the Basketball Hall of Fame.