The Corbomite Maneuver Balance of Terror What are Little Girls Made Of? Court Martial The Menagerie Shore Leave The Squire of Gothos Arena Tomorrow is Yesterday A Taste of Armageddon Space Seed The Devil in the Dark Errand of Mercy The City on the Edge of Forever
Season 2:
Amok Time The Doomsday Machine The Changeling Mirror, Mirror The Trouble with Tribbles Journey to Babel A Private Little War A Piece of the Action The Ultimate Computer Assignment: Earth
Season 3:
Spectre of the Gun The Empath The Tholian Web Day of the Dove Let That Be Your Last Battlefield The Cloud Minders Requiem for Methuselah All Our Yesterdays
TAS:
Yesteryear The Infinite Vulcan The Magicks of Megas-Tu Once Upon a Planet How Sharper Than a Serpent’s Tooth
I can elaborate on why these episodes are chosen but I’m afraid my comment would get too long.