Well, 10/4 is a showy piece in and of itself, but I'll bite.
I suggest Scarlatti 141 I agree with former posters - 10-4 is a great show off piece!
Ups, while reading replies to your original post I forgot you wanted something romantic or 20th century. How about Rachmaninoff's Moment Musicaux No 4? It always pleases audiences:-)
Here are some pieces that I do not want to play...Winter wind
A few that come to mind for me: Etude op 25 no 11- Chopin
A few that come to mind for me: Etude op 25 no 11- Chopin3rd movement of moonlight sonata - BeethovenHungarian rhapsody no. 2 -Liszt (longer than 6 minutes, but very impressive piece)Etude op. 8 no. 12- Alexander Scraibin If you're looking to learn a showy piece for non musical people, then learn pirates of the Caribbean or something.