Since everyone seems to be focusing on baseball, I'll add a few from other sports....
1955 Topps All-American - Jim Thorpe
1957 Topps - Johnny Unitas & Bart Starr RC's
1958 Topps - Jim Brown RC
1965 Topps - Joe Namath RC
1957-58 Topps - Cousy & Russell RC's
1961-62 Fleer - Chamberlain, Robertson, & West RC's
1969-70 Topps - Alcindor RC
1972-73 Topps - Erving RC
1979-80 Topps - Bird/Magic RC
1986 Fleer - Jordan RC
1954-55 Topps - Gordie Howe
1958-59 Topps - Bobby Hull RC
1966-67 Topps - Bobby Orr RC
1979-80 Topps/OPC - Gretzky RC
As for baseball, I'd have to go with the 53 Paige, 54 Aaron RC, and 55 Koufax RC.