My suggestions:
Beethoven's 31st and 32nd piano sonatas (probably the most beautiful music I have ever heard)
Beethoven's Razumovsky quartets (opus 59)
Bach's cantata 'Nun komm, der Heiden Heiland II'
Rachmaninov's Preludes (esp. no. 24, what a lovely piece of classical kitsch)
George Enescu's Sonatas for violin and piano
I could go on for a while, if you wish.