1) Fantasia on a Theme by Tallis -- Ralph Vaughan Williams
For String Quartet and Double String Orchestra
2) Piano Concerto No. 2 -- Sergei Rachmaninoff
For Piano and Orchestra (op. 18)
3) Piano Concerto No. 3 -- Sergei Rachmaninoff
For Piano and Orchestra (op. 30)
4) Folk Song Suite -- Ralph Vaughan Williams
For Concert Band
5) Piano Concerto -- Robert Schumann
For Piano and Orchestra (op. 54)
6) Toccata and Fugue in D minor -- J.S. Bach
For Organ
7) Polonaise-Fantaisie -- Fryderyk Chopin
For Piano (op. 61)
8) Hungarian Rhapsody No. 2 -- Franz Liszt
For Piano
9) Piano Concerto -- Edvard Grieg
For Piano and Orchestra (op. 16)
10) Slavonic Dances -- Antonin Dvorak
For either Piano Duo or Orchestra
Other Good Pieces:
-- Any Chopin Polonaise, and many of his Mazurkas and Nocturnes
-- Gustav Holst's First Suite (for Band) and The Planets (for large Orchestra)
-- John Zdechlik's Psalm 46 (for Band)
-- Paganini's Caprice No. 24
-- And, if any of you are interested in humour value, check out Arnold Schoenberg's Pierrot Lunaire.
In summary, if you couldn't tell from the above, my favourite composers are first and foremost, Ralph Vaughan Williams; shortly followed by Liszt, Chopin, and Rachmaninoff.
Now, of course, the point of this list is that you will go check out these pieces (and agree with me) ;-)