Ultima 7 Serpent Isle:
Dupre's scene in Monitor when you require a certain something extra to bind the Bane of Chaos's pieces together, then finding him again in Ultima 9. Good heavens, that just wrenched my wee heart out.
This will sound silly, but the
Final Boss of Super Metroid tends to bring me to tears a bit, every time. It's a classic
Eleventh Hour Superpower trope. You face off against Mother Brain in her second phase, and realize that not only are your attacks doing very, very little damage to her, but she's
utterly kicking your butt with her giant deadly rainbow brain beams. They do a metric boatload of damage and render you helpless on the floor for a bit after pinning you against the wall. You begin to feel utterly hopeless after all of these barrages of deadly energy.
When you're just about dead,
the little baby Metroid you had found from the previous game swoops in, drains Mother Brain's life, then flies away, ... and then has second thoughts, giving you back all of the life it had drained from Mother Brain.
Then Mother Brain slowly awakens, walking forward in anger, firing rings of energy at the large Metroid that's still in the process of saving your life. You watch as your Metroid savior turns from a bright healthy green to a dull weak brown, even as it continues to pour its energy into your life tanks. Eventually it lifts off of you, having done everything it can, and Mother Brain fires yet another beam of energy at you. The Metroid swoops back in just in time to take one last hit, dying for you in a series of saddening explosions, falling onto you as the screen goes black.
The music changes to the charmingly optimistic overworld theme. You realize that something is different. You open your inventory and all of your beams are gone - Replaced by a Beam weapon you had never picked up - The Hyper Beam. You fire the beam at Mother Brain and watch as a rainbow cylinder of concentrated energy careens from your arm cannon, and Mother Brain's head slams backward in well-earned terrifyingly strong whiplash.
You regain hope. The battle has turned to your favor, all thanks to the sacrifice of your little baby Metroid.
A surprisingly emotional moment for a final boss battle. Hot damn. They don't make games like they used to, folks!