8. The Doomsday Machine
The Enterprise finds one of its sister ships, the U.S.S. Constellation, dead in space, abandoned by its entire crew save her Commodore Matt Decker in a catatonic state. The ship's log reveals that the Constellation encountered a massive "doomsday" entity that crippled the ship and the crew, having abandoned ship and settled on a nearby planet, was obliterated after the device consumed said planet. The device, a "doomsday machine" of sorts, is believed to have been created to stop both sides of a distant war and the machine ventured into our galaxy after the conflict subsided, and uses the rubble from the planets it consumes as energy. After Decker sacrifices himself in a kamikaze mission into the center of the device via a shuttlecraft, the crew discovers that the internal explosion of the shuttlecraft managed to slow it down. Kirk and Scotty then move the Constellation directly into the path of the planet killer, hoping the much larger craft will result in the destruction or disabling of the device. Kirk becomes stranded aboard the doomed ship until the very last second when Scotty pulls him out and the planet killer is disabled, adrift in space just as the Constellation was.
7. The Squire Of Gothos
Felicitations and tallyho! In what is undoubtedly one of the finest (albeit more bizarre) hours of Star Trek, the Enterprise crew makes first contact with the Q continuum in the form of Trelane, played rather brilliantly by the late great William Campbell, also known for playing Captain Koloth. You read that right; if you read the canon novel "Q-Squared," you will see that Trelane was an early version of the Q, which honestly shouldn't be that surprising. The Enterprise is in the middle of a supply mission when a mysterious planet appears and Kirk and Sulu vanish, being held in suspended animation as keepsakes for the childish Trelane. After a futile attempt at escape, Kirk is sentenced to die by Trelane's hand, and after a sporting sword fight, one of the most bizarre endings in all television history occurs when Trelane's parents (that's right, his PARENTS) appear and basically put him to bed early for his shenanigans. Talk about anticlimactic...