From Wikipedia:
In a game against the Pittsburgh Pirates on September 20, 1992, he turned an unassisted triple play. In the sixth inning, Morandini caught a line drive off of the bat of Jeff King, touched second base to force out Andy Van Slyke, and tagged out Barry Bonds coming from first base; the Pirates went on to win the game, 3–2, in extra innings.[it was the first unassisted triple play since 1968, and the first in the National League since 1927. Morandini was also the first second baseman in National League history, and the first in the regular season, to turn an unassisted triple play; all previous occurrences were made by first basemen or shortstops. The only other second baseman to achieve the feat prior was Bill Wambsganss, who turned a triple play in the 1920 World Series.
I remember Harry Kalas calling it- he was beside himself!
Randy Ready could have had an unassisted triple play but he flipped to the 1B to get the 3rd out, even though the runner was 5 feet from him and he could have tagged him. That happened around 1990?? I don't recall.