The classical repertiore is so extensive, I think the most useful response is suggesting some mainstream and some non-mainstream works that might open doors for those unfamiliar or minimally familiar with classical . These works are not necessarily my favorites but they might work to get the novice started.
Traditional gateway works
Symphonic:
Beethoven symphonies 3,5, and 9.
Violin Concerto
Mahler symphonies 1, 4, and 9.
Strauss, Also Sprach Zarathustra
Stravinsky, Firebird and Petrushka
Tchaikovsky Violin Concerto
Brahms: Violin Concerto
Bruch Violin Concerto
Sibelius Violin Concerto
Chamber Music:
All Schubert Trios
Schubert string quintet in C, op163
Beethoven Moonlight, Pathetique, and
Apsionata piano sonatas
Beethoven Archduke Trio
Non traditional gateways that might
work, especially if you like driving rhythms or can tolerate some
dissonance.
Shostakovich, Cello Sonata #2
Beethoven Late String Quartets
Bartok String Quartets, especially 4,
5, and 6.
Stravinsky, Right of Spring, Duo
Concertante, and Violin Concerto
Also I recommend a book that is
probably over 40 years old, but a wonderful introduction to the basic
classical repertoire with recording recommendations:101
Masterpieces of Music and Their Composers by Martin
Bookspan
