I'd say late Beethoven Sonatas. I've made it my life goal to be able to understand late Beethoven.
That and Chopin 3rd Sonata.
I also want to play
Bach: Partitas, I never got to finish Bb major... maybe after auditions
Mozart: hmmm.. I don't have any ambitions with Mozart. I would love to play the 2 piano sonata with someone though.
Beethoven: late sonatas, as I said.
Schubert: sonatas, kinda like how I feel about Beethoven.
Chopin: 3rd Sonata, Barcarolle, Ballade 4 seem to be my goal pieces.
Liszt: Sonata, Mepisto waltzes
Schumann: Fantasie, Humoresque
Brahms: Piano concerti
Debussy: Poisson D'Or, the preludes
Ravel: Gaspard I guess, La valse, maybe Tombeau
Scriabin: Sonatas 4 and 5, concerto,
Rachmaninoff: 2nd Sonata,
Prokofiev: 2nd and 3rd concerto, Toccata, sonatas.