[One Winged Angel]

Ambient Angels is a fantastic choice if you can reliably FC it. You should definitely choose something that gets progressively more difficult over time so that you'll continue to wow your audience even as some of them start to think 'surely he can't go any faster than this'.

If you want to go hardcore climax theory, something like Destination of the Heart would definitely drop everyone's jaws as soon as the ending jumpstream takes off, but if you pick this be sure you can FC the 200bpm jumpstream most if not all the time.

Alternatively you could pick something technical with a lot of colours. A lot of my friends who don't play these games seem to think the more colours in the file, the crazier it is. We Wish You A Merry XMas (which, coincidentally, is also quite appropriate to pick this time of year) accomplishes this. But if you're going strictly for wow factor, my vote is for one of the former two since nothing beats tried and true climax theory.