When Shepherd Exalts as a Solar, and her vision from The Unconquered Sun. And later on, when Garrus Exalts as a Lunar and his own vision from Luna The Changing Lady. It's just such a tremendously powerful and beautiful moment, and some of the very best writing in depicting what it really means to be Exalted by the Celestia Incarna.
The fact that there are Quarians on Rannoch, protected by the geth says a lot about the geth's loyalty to the Creators.
Mordin curing the genophage. Even more heartwarming, doing so is enough to let him Exalt.