There are only two seasons in New York Mets history which included a batter slugging over .600. The first happened in 1998 when Mike Piazza finished the year with a slugging percentage of .607 as a member of the Amazins. Two years later, he set a new franchise high at .614 over the course of a full campaign.
Piazza is well-known as the greatest home run hitting catcher in MLB history. Although he never held the franchise or single-season record for round-trippers, one could still make an argument that nobody literally slugged baseball as well as him.