M-5: In the 1968 Star Trek: the Original Series episode called "The Ultimate Computer" the M-5 is installed on Enterprise for testing. Its goal is to radically improve the starship's capability in order to minimize the number of personnel on board. The M-5 works as expected except for a slight homicidal tendency. Oops. To make matters worse it is fully capable of protecting itself from outside interference. Fortunately, Kirk uses his great computer skills and talks the computer into killing itself.
(Image courtesy of Star Trek.com)