Now, this is hell of a challenge to pick... My top ten movements are constantly flowing back and forth, but there are a handful that always remain around the top. Of course, you'll quickly figure out what I tend to favor the most: Romantic and post-Romantic composers, Russians, orchestral pieces... And you'll be able to quickly point out what particular trends have carried on into my own music.
So I'm first listing the honorable mentions...
Rachmaninov, Piano Concerto No. 2, 1st movement.
Haendel: Messiah, "Unto Us a Child is Born".
Mussorgsky, Pictures at an Exposition, 10th movement ("The Great Gate of Kiev").
Bach, Orchestral Suite No. 3, 2nd movement ("Air"). Especially the non-historically-informed performances I grew up to love.
Beethoven, Symphony No. 5, 1st and 3rd movements.
Tchaikovsky, The Maid of Orleans, Act III, Scene 2, "March". Rivalling Verdi's better known march from Aida.
Tchaikovsky, Eugene Onegin, Act I, Letter Scene.
Tchaikovsky, The Maid of Orleans, Act I, Hymn.
Rachmaninov, Symphony No. 2, 1st movement.
Elgar, Enigma Variations, "Nimrod".
Tchaikovsky, Symphony No. 4, 1st movement.
Tchaikovsky, Manfred Symphony, 2nd movement.
Tchaikovsky, Symphony No. 5, 2nd movement.
Mahler, Symphony No. 1, 1st and 4th movements.
Mendelssohn, Violin Concerto in E minor, 1st movement.
Dvorak, Symphony No. 7, 3rd movement.
Tchaikovsky, The Sleeping Beauty, Act I (Rose Adagio) and Act III (March, Polonaise and Pas de Quattre).
Prokofiev, Romeo and Juliet, Act I, "Dance of the Knights".
Beethoven, Symphony No. 9, 1st movement.
Mozart, Great Mass in C Minor, "Kyrie".
Shostakovich, The Gadfly, "Romance".
Morricone, Cinema Paradiso, "Love Theme".
Brahms, Symphony No. 1, 4th movement.
And now, the top ten, in (some sort of) descending order, with a few extra comments...
10) Borodin, String Quartet No. 2 in D, 2nd movement. What a lovely nocturne!
9) Mozart, Symphony No. 41 in C, 4th movement. Ah, that five-theme fugue...
8) Prokofiev, Piano Concerto No. 1 in Db, 1st movement. Has blown me away every time since I first heard it.
7) Beethoven, Symphony No. 7, 1st movement. It always gets me bouncing in my seat with its infectious rhythms.
6) Delius, Florida Suite, 1st movement ("Daybreak")
5) Mahler, Symphony No. 4, 1st movement. Couldn't avoid falling in love with it at once.
4) Grofe, Grand Canyon Suite, 4th movement, ("Sunset"). Rather than the more famous "On the Trail".
3) Tchaikovsky, The Queen of Spades, Act III, Scene 2. I just love the way the drama is enhanced by the music in this passage.
2) Mahler, Symphony No. 2, 1st movement. An epic, gigantic funeral march.
1) Tchaikovsky, Symphony No. 6 (Pathetique), 3rd movement. It... just brings the house down!