Man, I hope you're pulling my chains.
Show off pieces? Man...these are NOT show off pieces AT ALL.
First of all, a "showpiece" implies emptiness, vacuity. There are some pieces with gargantuan difficulties that do not qualify as "show off pieces" because they are substantial and formidable bodies of piano literature, such as the Liszt B minor sonata, Alkan Symphony, Medtner Night Wind, Scriabin Sonata 7, etc.
If you are looking for a simple "showpiece" I might recommend a few. Note how NONE of them are by Mozart, Beethoven, Chopin, Schubert, Bach, Rachmaninoff, Scriabin, Medtner, Alkan, Saint-Saens, Henselt, etc...
Dohnanyi Concert Etude No. 6 in F minor "Cappriccio"
Liszt Feux Follets
Liszt La Campanella
Balakirev Islamey
Villalobos Rudepoêma
Notice how these pieces revolve around ostentatious virtuosity.
~Max~