Hmmm, quite a few moments come to mind. Like many people here, Village Bridge is amazing when you get all the musicians contributing to the music. I even learned the lyrics at one point, haha!
I also remember standing in awe of Route 10's music. Route 23 is great too. Both have a different feel to them, yet are appropriate for being the final route before Victory Road, considering the events that have transpired up to that point.
But one of my fondest memories is probably the unveiling of the statue at Pokéstar Studios after all that time starring in films. And then getting to see that one room with all the punny movie script titles. :P