Mine are the following...

The ending of A Realm Reborn when Merlwyb, Kan-E-Senna, and Raubahn shouted in synchrony "A REALM REBORN!"

Any and every encounter with the Warriors of Darkness, including the very first one where they showed the leader of them on the moon.

Ending of Stormblood when you defeat Shinryu. And then Lyse and the others began singing the Ala Mhigo anthem. I adore the part where Lyse slowly raised her hand when the song went "Raise up your hands and voices".

What about you?