|T-Men (1947) [Tony Genaro a.k.a. Tony Galvani]: Shot to death by John Wengraf.
The Dupont Show of the Month: Billy Budd (1959) [Claggart]: Killed with a single blow to the head by Don Murray. (I haven't seen this version, but I'm familiar with the story.)
Hamlet (1964) [Hamlet]: Stabbed with a poison-coated sword during a fencing match with Laertes. (The IMDB doesn't identify who played Laertes in this version.) He dies shortly after killing Howard Da Silva in turn.
Star Trek: The Man Trap (1966) [Professor Robert Crater]: Salt drained from his body (off-screen) by the alien (Jeanne Bal/Sharon Gimpel) in the sickbay; his body is shown afterwards when Grace Lee Whitney and William Shatner discover him.