Den of Geek tackles the question of the 10 Essential TOS Episodes
Man Trap, Let That Be Your Last Battlefield, Arena, Balance of Terror, Space Seed, A Piece of the Action, Devil in the Dark, The Corbomite Maneuver, The City on the Edge of Forever, A Taste of Armageddon
I'm not so sure about this list. A Piece of the Action is fun, but I'm not sure about essential. I'm not sure if Tribbles belongs in this list, but it's a consideration. I have no clue why Journey to Babel isn't in this list. I'd also put Conscience of the King above some of the episodes on this list.
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mudshark: Nate's just being...Nate.
Zeke: It comes
nateurally to him.
mudshark: I don't expect Nate to make sense, really -- it's just a bad idea.
Sa'ar Chasm on the 5M.net forum: Sit back, relax, and revel in the insanity.
Adam Savage: I reject your reality and substitute my own!
Hanlon's Razor: Never attribute to malice that which can be adequately explained by stupidity.
Crow T. Robot: Oh, stop pretending there's a plot. Don't cheapen yourself further.