For me he'll be remembered for that incredible Columbo episode "A Stitch in Crime" (1973). In that one Nimoy was dark scary and totally believable as a cld-blooded killer.
not a fan of startrek but only last sunday night i watched him about to check out of life in the classic science fiction/horror movie invasion of the body snatchers.
I've been collecting the DVDs of the U.S. TV show Get Smart, and before becoming famous for Star Trek Leonard Nimoy played a KAOS agent named Stryker in an episode from season 1 (air date: January 22, 1966) called The Dead Spy Scrawls in 1966.
In The Man From U.N.C.L.E episode "The Strigas Affair", Nimoy and Shatner play adversaries a good two years before Star Trek. Kind of a cool coincedence.