M-4: M-4 was another robot found in the Star Trek: The Original Series episode "Requiem for Methuselah". M-4 was
Flint's guard-bot and
gofer (and looked a bit like the psychotic satellite Nomad). M-4 witnesses Kirk
kissing Rayna and as it is about to attack the captain when Spock destroys it
with a well place phaser blast. Isn't that the way of life -- you are about to
make out with a sexy android and a killer robot comes along and ruins everything.
(Image courtesy of Memory Alpha)