No lumps in the throat or teary eyes, but one of the better character moments comes in "Bread and Circuses" between McCoy and Spock locked in a cell, separated from Kirk.
MCCOY: Do you know why you're not afraid to die, Spock? You're more afraid of living. Each day you stay alive is just one more day you might slip and let your human half peek out. That's it, isn't it? Insecurity. Why, you wouldn't know what to do with a genuine, warm, decent feeling.
SPOCK: Really, Doctor?
MCCOY: I know. I'm worried about Jim, too.
The chemistry between Kelley and Nimoy is in full play.
And Edith's death in "The City on the Edge of Forever" really juices it up by letting us know when it's about to happen.