This new forum section has shown to be a pretty good idea. I guess I'll contribute by adding a classic, one of the "Three B's": Beethoven.
For a while my exposure had mainly been limited to his symphonies, sonatas and concertos. After that, I discovered just how much more there really is out there.
Outside of the "main" repertoire (symphonies, concertos and sonatas), some favorites include:
Choral Fantasy in C minor
The Consecration of the House
The Ruins of Athens
Wellington's Victory (hard to ignore)