My vote: The 25 most important people in baseball history.

My list, sorted by first name, was originally 29 (4 "dropped" but shown), heavy on stats guys:

Babe Ruth  Great pitcher, then the greatest home run hitter and entertaining.
Barry Bonds  Second greatest home run hitter and entertaining but obnoxious.
Bartlett Giamatti  Commissioner who banned Pete Rose for gambling; good.
Bill James  Biggest influence on stats.
Branch Rickey Farm system and modern racial integration.
Buck O'Neil  dropped; shook hands with him at the 1995 Babe Ruth symposium at Hoftra University.
Bud Selig - worst commissioner; ruined baseball.
Cal Ripken Jr  "saved" baseball after the disastrous aborted 1994 season by breaking Gehrig's record for consecutive games played.
Casey Stengel  dropped
Colonel Jacob Ruppert  made the New York Yankees the most dominant team on the planet.
Curt Flood  started the ball rolling towards free agency.
Dave Smith  Founded retrosheet.org
Dr. Frank Jobe  Saved the career of pitcher Tommy John and countless others.
Dr. Harold Seymour  early researcher
Honus Wagner  dropped
Jackie Robinson  Broke the modern color line and with style.  An American hero.
Jim Bouton  Wrote "Ball Four", which revealed many unknowns and changed baseball writing.
John Dewan  stats guy
John Thorn  historian
Jose Canseco  Broke open the steroids story by revealing his own use.
Kenesaw Mountain Landis  First commissioner who took decisive action on the gambling problems that threatened the integrity of the game.
Lou Gehrig  Tragic figure who gave the baseball Gettysburg address.
Marvin Miller  Made the players union powerful and changed the relationship with the owners.
Mel Allen  dropped
Oliver Wendell Holmes Jr.  Supreme Court justice who ruled on baseball's anti-trust exemption.
Ozzie Smith  Revolutionized play at shortstop and did pre-game back flips.
Sadaharu Oh  Holds the pro record for most career home runs.
Sean Lahman  I bequeathed the name of my 1990s Windows Baseball Database to Sean for use on his site, from which we can get current data for research on all players from the beginning of time.
Walter O'Malley  Expanded major league baseball into a geographically national sport.

José Canseco with the Worcester Tornadoes May 14, 2011 by Bryan Horowitz via Wikimedia Commons