Spoiler
House, Yes Man, Caesar, Vulpes Inculta. So well set-up, and then mind blowing what you learn about the world. You don't get to talk with Kimball, but his speech scene is so great on so many levels it's awesome too.
Every single one of the companions' (the human/former human ones, anyway) stories. They all touched my heart and some had so much loss in them they made me cry.