My vote goes towards the entire palace subterfuge and escape sequence. Not only are we introduced to Balthier and Fran, I just like how it quickened the pace of the, admittedly slow opening portion of the game. Even the Barheim Passage, probably the most ponderous portion of this sequence had a good share of moments.

I also like the Sandsea. Not so much traversing the Sandsea, but it was cool to finally get all the characters together for the first time.