What are your top three favorite classical compositions?

Three!? Seriously!

I could never narrow it down to just three, even 10 wouldn't be able to cover all the classical music I rate equally highly. So, I will have to cheat. 😉

I am only into: 20th century, atonal, serial, avant-garde classical music. Mostly from post 1950 to the present.

Alban Berg - Violin Concerto 

Elliott Carter - Concerto for Orchestra 

Charles Wuorinen  - 4th piano Concerto 

Joan Tower  - Concerto for Orchestra 

Ernst Krenek - Static and Ecstatic 

Magnus Lindberg  - Sculpture

And a few, less 'thorny' sounding pieces:

Bartok - Music for strings, percussion, celesta

Samuel Barber - Piano Concerto 

Stravinsky - The Rite of Spring 

Again, there are many other pieces that I rate as highly as those I listed. If I made this list tomorrow, it could be almost completely different. 

Bach Goldberg variations, Elgar enigma variations, Beethoven’s seventh Symphony

Out of thousands, you jest! But I do seem to listen more often to solo piano music by Chopin, Debussy, Beethoven, Brahms, Schubert, Schumann, and Prokofiev than most others. 

How about you?

You’re right!  
Three is a near impossible task. And, as was said, it might be different tomorrow. 
 But, here goes:

 Mahler 9th Symphony 

Mozart Requiem

Almost any Mozart Piano Concerto (cheating)