Star Wars: The Old Republic/Tear Jerker

General

• The Exile's death. After an entire life full of pain, manipulations and deceit, she gets stabbed in the back by Scourge to prevent her from saving Revan. Read Revan for more details.
• The moment in the "Return" trailer when Satele Shan senses her Master's death.
• Initially, the quest to discover the fate of the Exiles on Taris is almost hopeful, and even after you find out there struggles, you still hold out hope that you're going to find their descendants. But as you read the increasingly bleak apocalyptic logs, this gradually turns to general depression, and the last log is downright heartbreaking.

Jedi Knight Storyline

Jedi Consular Storyline

Trooper Storyline

• The Trooper's class quest on Tatooine culminates in a Sadistic Choice: let the Imperials escape with state-of-the-art new bomb designs that they plan to test on civilians on some other frontier world, or let your former teammate - the man who gave you the warning about what the Imperials were doing and gave you the chance to stop them in the first place - die when the base self-destructs. There's not enough time to stop the explosion and still catch the Imperials, and he begs you to leave him behind and go after them; if you do, the game shows him in his cell as the base blows, sadly resigned to his fate.

Smuggler Storyline

Sith Warrior Storyline

• If you play as a female Sith warrior and marries Quinn, one of his love letters to you is about one having children together one day (or in his own words, an 'infant contingency report'). In which he writes in formal military language about the risk of you being weakened during the pregnancy, how to protect the infant against your enemies once he or she is born, etc. Although it is heartwarming in a way, it also highlighted the fact that despite all your power and authority, as a powerful Sith, you will never be able to enjoy a happy family life the same way that a normal person can and have to be constantly at guard against everyone that want to harm your loved ones.

Sith Inquisitor Storyline

Bounty Hunter Storyline

Imperial Agent Storyline

• The endgame of Chapter 3 is bleakly depressing, in a way. After chasing the Star Cabal for a chapter and a half, you finally get your confrontation with Hunter. What you're faced with is someone who never really had a chance; someone so utterly screwed up by life that the Agent is the closest thing she has to a friend. And once it's all over, it's likely no one will ever remember her, save for the Agent and their crew. The scene is heartbreaking, as is one of the Agent's potential goodbyes (the VAs manage to make the unlikeliest of lines sound comforting):

You were the best enemy I could have wished for.