I'll just assume people realize spoilers will be in this thread.

FFI - Learning Garland is Chaos.

FFII - I'll take a guess and Say Leon rejoining you.

FFIII - No Idea

FFIV - Tellah Vs. Golbez did it for me.

FFV - Definatley Galif's Final hurrah. He kicked so much ass.

FFVI - Kefka offing Ghestal and leveling the planets surface.

FFVII - Not really sure, I beat it, but I got nothing.

FFVIII - No comment.

FF IX - I feel there were 2 moments that really defined the Game more than others. The coming of Black Waltz #3, and the arrival of Trance Kuja.

FF X - When Auron is revealed to be a ghost.