Nomad: In the 1968 Star Trek: the Original Series episode called "The Changeling" a mysterious space probe is beamed aboard the Enterprise after it has wiped out all life on a planet in the Malurian star system. The probe, Nomad can fire incredibly powerful energy bolts and can absorb anything the Enterprise can throw at it. Fortunately, Nomad thinks Kirk is "the creator". Unfortunately Nomad, originally an Earth space probe, had a mid-space collision with an alien space probe called Tan Ru and has been on a universe-wide life form eradication mission since. Fortunately, Kirk has a strong background in computer engineering and talks Nomad into killing itself.
(Image courtesy of Memory Alpha)