A few of my favourites (I'll try to ignore large scale works except a few necessary.):
From Bach:
Goldberg Variations
(Siciliano in G minor
Ich ruf zu dir, Herr You can find Tatiana Nikolayeva's performances easily.
Wacht auf, ruft uns die Stimme)
Chromatic Fantasy and Fugue (Note that Gould only plays the Fantasy)
Prelude for Lute in C minor
Double Violin Concerto
Wir sitzen mit Tränen nieder from St. Matthäus Passion, the best in the whole thing.
Chaconne from The Partita for Solo Violin in D minor and the Busoni transc. (I recommend Perlman for one and Berman for the other)
Prelude and Fugue C# minor, D minor, C minor from Book One and G# minor, A minor and F# minor from Book Two.
From Mozart:
Piano Concerto No. 20
Masonische Trauermusik
Piano Sonata No. 8 in A minor
Schubert:
Auf dem Wasser zu singen (Liszt transcription, the song sucks.)
Der Erlkönig (The song. Liszt transcription doesn't suck, but the poem is too good to be ignored, as long as you speak German of course.)
Der Tod und Das Mädchen
String Quartet No. 14 (Also titled Der Tod und Das Mädchen)
Sonatas
Schumann:
Carnaval
Fantasiestücke
Kreisleriana
Études Symphoniques
Chopin:
Ballades, especially the famous first and the fourth
Scherzi, especialy the second and the third
Preludes, esp. D minor, G minor, F minor, F# minor, C minor, Db major, E minor
Etudes, esp. Op. 10 No. 1, Op. 10 No. 4, Op. 10 No. 9, Op. 10 No. 12 and all of op. 25
Mazurkas, Waltzes and Nocturnes, which you have to discover on your own
Mahler:
Symphony No. 9
Symphony No. 5
Das Lied der Erde
Medtner:
Fairy Tales. A 16 or 17 minutes long video of Berezovsky playing a few can be found on youtube, which will be enough.
Rachmaninoff:
All piano concerti (3>4>2>1)
Symphonic Dances
Die Toteninsel
Preludes, especially B minor, D major, A minor, C minor and G# minor
Etudes-Tableaux, esp. 39-3>39-2>33-3>33-5>33-9>39-6
Moments Musicaux
Second Piano Sonata
Suite for Two Pianos No. 2
Trio Elegiaque No. 2
Debussy:
Preludes (Gieseking recording is essential for any music lover IMO.)
La Mer
Beethoven:
3rd, 5th, 7th, 9th symphonies.
Piano Sonatas. The ones with the titles are obviously more appreciated and two of the set suck, frankly.
Mendelssohn:
Fingal's Cave Ouverture
Rondo Capriciosso
Shostakovich:
Preludes and Fugues Op. 87, most of the minor ones with E minor, F# minor, C# minor, G# minor and D minor being my favourites, and Db major
String Quartet No.8 (And the chamber symphony)
Strin Quartet No. 13
String Quartet No. 15
Piano Trio No. 2
Symphonies, all of them are good, except the Haydnesque 9th, 5th and 10th are popular, and the 7th is a favourite of mine.
Piano Sonata No. 2
Some early piano works.
Prokofiev:
Symphonies
Toccata
Piano Concerti, esp. 2 and 3
Violin Concerti.
Sonatas, esp. 7th, along with the other war sonatas.
Mussorgsky:
Pictures at an Exhibition
Korsakov:
Scheherazade
Ravel:
Gaspard de la Nuit
Carl Vine:
Piano Sonata
Arvo Pärt:
Te Deum
Silentium
Spiegel im Spiegel
Für Alina
Cage:
Dream
In a Landscape
Liszt:
Mazeppa
Totentanz
Benediction de Dieu dans la solitude
Mephisto Waltz No. 1
Piano Sonata in B minor
Funerailles
Consolations, esp. third.
The Troisieme Annee de Pelerinages
Ballade No. 2
Tchaikovsky (I don't like his piano music.):
Symphonies, esp. 1-4-6
Violin Concerto
Borodin:
In the Steppes of Central Asia
Alkan:
Op. 39
Barcarolle
Mad Woman thing
Le Festin d'Esope (Kidding)
Brahms:
Rhapsody in G minor
Ballade in G minor
Op. 116-119
BTW Stanchinsky Sonata is really amazing, his preludes are even amazinger(too cool to write it the correct way).
These should keep you busy (I know there are lots of large scale works.)