Note: I got many of these athletes from a calendar with lefty information and I'm not sure whether some of the people listed (especially baseball players) are mostly right-handed but have played with their left hands once-in-a-while. Please e-mail me if you see any people listed here that you know are not left-handed.
Earl Anthony (b. 1938), U.S. championship bowler
Nate Archibald, basketball player
Steve Avery, U.S. baseball player
Yogi Berra, U.S. baseball player
Larry Bird (b. 1956), U.S. basketball player
Nicole Bobek, U.S. figure skater
Wade Boggs, baseball player
Barry Bonds, baseball player
Bill Bradley, basketball player and U.S. Senator
George Brett, baseball player
Lou Brock, baseball player
Brett Butler, baseball player
Rod Carew, baseball player
Steve Carlton, U.S. baseball player
Bob Charles, golf player
Will Clark, baseball player
Ty Cobb (1996-1961) U.S. baseball player
Jimmy Conners (b. 1952), U.S. tennis player
James Corbett (1866-1933), U.S. heavyweight boxing champion
Patty Costello (b. 1947), U.S. championship bowler
Dwight F. Davis (1879-1945), U.S. founder of the Davis Cup
Bill Dickey, baseball player
Lenny Dykstra, baseball player
Phil Esposito, hockey player
Lou Gehrig (1903-1941), U.S. baseball player
Tom Glavine, baseball player
Vernon "Lefty" Gomez (1908-1989), U.S. baseball player
Ken Griffey, Jr. , U.S.???
"Lefty" Grove (1900-1975), U.S. baseball player
Tony Gwynn, baseball player
"Marvelous" Marvin Hagler, boxer
Dorothy Hamill (1903-1988), U.S. skating champion
Ricky Henderson, baseball player
Keith Hernandez (b. 1953), U.S. baseball player
Ben Hogan (b. 1912), U.S. golf pro
Carl Hubbell (1903-1988), U.S. baseball player (pitcher)
"Shoeless" Joe Jackson, baseball player
Reggie Jackson (b. 1946), U.S. baseball player
Bruce Jenner (b. 1949), U.S. decathlon athlete
Tommy John, U.S. pitcher
Wally Joyner, baseball player
David Justice, baseball player
Bob Kipper, baseball player (pitcher)
Sandy Koufax (b. 1935), U.S. baseball player
John Kruk, baseball player
Tommy Lasorda (b. 1927), U.S. baseball manager
Rod Laver (b. 1938), Australian tennis champion
Henri LeConte, tennis player
Kenny Lofton, baseball player
Greg Louganis (b. 1960), U.S. Olympic diver
Willie McCovey (b. 1938), U.S. baseball player
John McGraw, baseball player
Fred McGriff, baseball player
Kevin Maas, basketball player
Joe Magrane, baseball player (pitcher)
Heinie Manush, baseball player
Dave Martinez, baseball player
Don Mattingly, U.S. baseball player
Stan Musial (b. 1920), U.S. baseball player
Thomas Muster, Austrian tennis player
Martina Navratilova (b. 1956), Czech-U.S. tennis champion
Paul O'Neill, baseball player
Sadaharu Oh, Japanese baseball star
Manuel Orantes (b. 1948), Spanish tennis champion
Mel Ott, baseball player
Rafael Palmeiro, baseball player
Pele (b. 1940), Brazilian soccer player
Willis Reed, basketball player
Brooks Robinson (b. 1937), U.S. baseball player
David Robinson, U.S. basketball player (San Antonio Spurs)
Bill Russell (b. 1934), U.S. basketball player
Babe Ruth (1895-1948), U.S. baseball player
Deion Sanders, baseball and football player
Terry Sawchuck, hockey player
Gayle Sayers, football player
Vin Scully (b. 1927), U.S. sports broadcaster
Monica Seles, tennis player
Gary Sobers (b. 1936), international cricket champion (from Barbados)
Warren Spahn (b. 1921), U.S. baseball player
Mark Spitz (b. 1950), U.S. Olympic swimmer
Ken Stabler (b. 1945), U.S. football player (QB)
Casey Stengel (1891-1975), U.S. baseball manager
Darryl Strawberry, U.S. baseball player
Roscoe Tanner (b. 1951), U.S. tennis champion
Fernando Valenzuela (b. 1960), Mexican-U.S. baseball player
Andy Varipapa, bowler
Guillermo Vilas (b. 1952), Argentinian tennis champion
