The cruel way Deckard completely undresses Rachael's humanity, recalling memories no one else could have known had she been a real human. The way she throws away her treasured photo of herself and her mother is heartbreaking.
Zhora's retirement. It emotionally sets up Roy's reprieve of Deckard. The song played during this scene, "Blade Runner Blues", also helps give the scene its mood.
Roy Batty's famous soliloquy at the end is very poignant.
Roy: I've... seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched c-beams glitter in the dark near the Tannhauser Gate. All those... moments... will be lost in time, like tears... in... rain. Time... to die...
Roy tearing up over Pris' corpse and giving her one final kiss after Deckard shoots her dead.