For me:
End of TWOK, as Kirk says he feels young, while the crew looks on at the new planet Genesis
End of TSFS, as Spock slowly recognizes Kirk and crew
End of TVH, as the crew is brought to the Enterprise-A
End of Nemesis: the surviving crew toasting Data, then the final scene of B4 and Picard.
TOS, Requiem for Methuselah
"Forget"
TNG, The Inner Light
Picard receiving the flute from Riker, then playing it alone.
DS9, In the Pale Moon Light:
"So... I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again, I would. Garak was right about one thing, a guilty conscience is a small price to pay for the safety of the Alpha Quadrant. So I will learn to live with it. Because I can live with it. I can live with it... Computer, erase that entire personal log."
Voyager: Drone
As One is dying, 7 of 9 pleads with him to live, saying "you are hurting me." Then, after his demise, 7 of 9 goes to the cargo bay by herself and reflects on his death.
Enterprise: Similitude
The funeral for Sim.