Here is my non-canonical list of major leaguers who have played a game in all 30 of the current parks in use. The first six players are on Washington. Unless noted, every player's 30th park was the new Nationals Park. And starting next year with new parks for the Yankees and Mets, we will wipe this slate clean until the Yankees-Mets interleague series.
Feel free to make additions or tell me if I need to delete someone:
Brian Schneider (Yankee Stadium)
Moises Alou (Yankee Stadium)
Chipper Jones (Angel Stadium)
Chris Gomez (Miller Park)
Jerry Hairston, Jr.
Mark Kotsay (Busch Stadium)
Marlon Byrd (Yankee Stadium)
Doug Mientkiewicz of Pittsburgh has not played in Petco Park. Jamie Moyer has not played in Great America Ball Park. Gabe Kapler has not played in Citizens Bank Park. Russ Springer, who has been in the majors since 1992, has never pitched in Progressive (formerly Jacobs) Field. Vicente Padilla has never played in the current Busch Stadium. David Weathers has never pitched at Tropicana Field.