10. The Devil In The Dark
In what William Shatner praises as the best episode of the original Star Trek, Kirk, Spock & McCoy are sent to investigate fifty strange deaths at a mining colony at Janus VI. Whatever killed the miners is also stealing equipment; if a critical piece to the facility's reactor isn't found or replaced within 48 hours, the entire mine will be rendered uninhabitable. Spock discovers that the killer is a silicon-based life form that calls itself a Horta and looks like Pizza the Hut from Spaceballs. The creature is the last of its kind and has been killing the miners and sabotaging the equipment in an effort to protect its eggs from harm. After Spock mind melds with the creature, the miners and the Horta come to a truce to stay out of each other's way while preserving the eggs and continuing the mining expeditions elsewhere.
9. The Changeling
No redshirt is safe, not even Scotty who is actually killed in this episode where the Enterprise intercepts the Earth probe known as Nomad after it decimates an entire star system. The device only shows mercy on the Enterprise and her crew because it mistakenly believes that its creator, scientist Jackson Roykirk, is ships captain. While a rather incompetent redshirt analyzes it, Nomad leaves the room and sneaks onto the bridge, where he kills Scotty and wipes Uhuras knowledge, practically leaving her a drooling vegetable, which Ive tried very very hard for years not to laugh at. Through the use of a Vulcan mind meld, Spock (whom Nomad hilariously sees as the only sophisticated lifeform aboard) discovers that the unit collided with another probe of greater power, one meant to sterilize soil samples, and Nomads subsequent metacrisis confused itself into thinking its purpose was to eradicate all inferior life. Kirk manages to instill another metacrisis within Nomad, making sure it knows that he is not Jackson Roykirk and therefore Nomad is just as imperfect as humans and must be destroyed. Shortly after being beamed out into space, Nomad self-destructs, but not before reviving Scotty of course.