I'm looking for suggestions on a particular piece that would have the biggest "wow" effect when played in front of a group of regular people. I would think brevity is important, as anything over 5 minutes and the crowd might get restless, have a melody that would be somewhat familiar, and definitely be flashy. The only necessity is perceived difficulty.
My vote would go for the Horowitz transcription of Wedding March and Variations. You have jumps, giant chords, and it's fast. Flight of the Bumblebee is a big crowd pleaser too.