If you can handle Chopin Sonata No. 3, Ill just go ahead and say some crazy difficult pieces.
Some big crowd pleasing Liszt transcriptions to think about:
Bellini-Liszt: I Puritani (18 min)
Bellini-LIszt: Grand Concert Fantasy from Sonnambula (15 min)
Auber-Liszt: La Muette De Portici - Tarantella di Bravura (9 min)
Gounod-Liszt: Waltz from Faust (10 min) {This one is really fun to play}
or the second Ballade (coz the first sucks!)
Do the First!! 2nd is overplayed and popularized by horowitz while the 1st is underrated and a masterpiece in its own right.
I second ilovexenakis and say you should look at Tannhauser Overture. It is just one of the greatest works I can think of as a grand scale concert piece. If you pull it off, the crowds will roar and victory will be yours.
BRAHMS: RHAPSODIES 1 AND 2
I was at a competition and the rhapsodies were considered staple pieces that everyone performs in front of adjudicators just to prove they can play. Since then, I cant recommend people play them if they want to be remembered for a particular performance. It's as ridiculous as playing pieces like Fantasy Impromptu and Fur Elise and expecting a standing ovation. These things just dont happen. You need to play something amazing- either a) something they have never heard before or b) a well known work, played so well they will think the composer has posessed you. Most of the time, you have to take it over the top without pissing anyone off. This is so difficult to do.. I dont know much, but I know it will probably not happen with the Brahms Rhapsodies or similar pieces.
I find the Liszt polonaises annoying after a while, kind of like one of those cell phone ring tones. You hear it once, you cant forget it because it's so annoying, and the last thing you want is to get flogged with it for 10 minutes.
I know I focus on Liszt alot, so lets think about others, in case you dont swing that way....
Scriabin Sonata No. 4 is beeeaaautiful! To me, the scriabin sonatas following it are getting into the contemporary period with strange harmonies and rhythms. But No. 4 is still very much late romantic in my opinion. I listen to it and still think of it as I think of Liszt or Rachmaninoff.
Heyyyy rachmaninoff!! I know Rach 2 concerto is overplayed so bad, but everyone loves it anyway. But now were getting into the golden age instead of the romantic age.
Ill think of some more..
donjuan