"All I ask is a tall ship and a star to steer her by. You could feel the wind at your back in those days, the sounds of the sea beneath you and even if you take away the wind and the water, it's still the same. The ship is yours, you can feel her. And the stars are still there, Bones..."

Kirk to McCoy
Source: John Masefield, 'Sea Fever'
TOS / The Ultimate Computer

"After all these years among humans...you still haven't learned to smile."
"Humans smile with so little provocation."

Amanda and Spock
TOS / Journey to Babel

"What do you call those?"
"I call them ears."
"Are you trying to be funny?"
"Never."

Flavius and Spock
TOS / Bread and Circuses

"I can't change the laws of physics."

Scott to Kirk
TOS / The Naked Time

"Interesting. Where would you estimate we belong, Miss Keeler?"
"You? At his side, as if you've always been there and always will."

Edith and Spock, on Spock and Kirk being out of place in early twentieth-century earth
TOS / The City on the Edge of Forever

"I've never understood the female capacity to avoid a direct answer to any question."

Spock to Leila
TOS / This Side of Paradise

"Knowledge, sir, should be free to all."

Harry Mudd to Spock
TOS / I, Mudd

"He gave his life in an attempt to save others. Not the worst way to go."

Kirk to Spock, on Commodore Matt Decker
TOS / The Doomsday Machine

"Do you know what you get if you feed a Tribble too much?"
"A fat tribble?"
"No. You get a whole bunch of hungry little Tribbles."

McCoy and Kirk
TOS / The Trouble with Tribbles

"I signed aboard this ship to practice medicine, not to have my atoms scattered back and forth across space by this gadget."
"You're an old fashioned boy, McCoy."

McCoy and Kirk, preparing to transport TOS / Space Seed