There have been only twelve unassisted triple plays in the over-137 year history of baseball. See Rafael Furcal Signs the Unassisted Triple Play Baseball, a part of Seth Swirsky's Baseball Collection.
Watch the video of my day at Angels Stadium where Asdrubal was kind enough to sign the one baseball that has every other Unassisted Triple Play-maker on it.
Seth Swirsky shot this video at Shea Stadium in August 2006. See Mookie Wilson, Keith Hernandez and the baseball that went through Bill Buckner's Legs.