Star Trek: The Original Series/Tear Jerker

Tear Jerkers in  include:

"Decker: I stayed behind. The Captain... last man aboard the ship; that's what you're supposed to do isn't it? And then it hit again, and the transporter went out. They were down there, I'm up here... Kirk: What hit? What attacked you? Decker: They say there's no devil, Jim... but there is -- right out of hell, I saw it! Kirk: Matt, where's your crew? Decker: On the third planet. Kirk: There is no third planet. Decker: (sobbing) Don't you think I know that? There was, but not anymore! They called me, they begged me for help -- four hundred of them! I couldn't... I-I couldn't..."
 * Commodore Decker's epic breakdown in "The Doomsday Machine" as he relates the Planet Killer's assault on his crew.

"T'Pau: Live long and prosper, Spock. Spock: I shall do neither. I have killed my captain and my friend."
 * "City on the Edge of Forever" definitely goes for the heartstrings. The original screenplay by Harlan Ellison was even more of a tearjerker, especially thanks to the inclusion of a legless World War I veteran called Trooper who is murdered as a result of the Enterprise crew members' presence in the past. Unlike Edith Keeler's survival, Trooper's death doesn't affect the time stream, and Kirk's reaction to the idea that the poor guy's life didn't matter is wrenching.
 * "The Immunity Syndrome": after Spock is chosen over Bones for the dangerous mission, Bones walks him down to the hanger deck, and Spock tells him, with just a touch of sarcasm, "Wish me luck." Bones refuses to say it until Spock is out of earshot. Later, when Spock's mission seems to have turned into a suicide run, Spock calls over the comm, "Tell Dr. Mc Coy he should have wished me luck." The look on Bones's face...
 * "Amok Time":

Dammit, Spock.
 * "The Naked Time" when Spock is under the influence of a virus that removes his inhibitions, and he breaks down crying that his mother never got to hear "I love you".
 * In a similar vein, Spock's ending words in "This Side of Paradise" about his time as part of the Lotus Eating Machine: "I have little to say about it, Captain. Except that, for the first time in my life, I was happy."
 * "Where No Man Has Gone Before," had Elizabeth Dehner's death.
 * I would say that Gary Mitchell's death from the same episode was also heartbreaking. He was essentially Kirk's brother (making his absence from the 2009 movie both annoying and painful) with both men forced to turn on each other; Kirk to protect his beloved ship and crew and Mitchell intoxicated and corrupted by godlike power that he never asked for; especially evident during his few brief moments of lucidity near the end of the episode, where both times, all the poor man can say is his best friend's name.