Bacholyte

Bach!

And who would want to be without many of the others already listed?

Rachmaninoff, Sibelius, and Scriabin (late piano music, at least) are sadly under-rated. When I mentioned that Sibelius lived to a ripe old age but composed only during the first half of his life, a friend once said, "We're grateful." But isn't he now on the verge of a revival?

Just to add a few more unusual-- I'm inordinately fond of:

Charles Tournemire (precurser of Messiaen)
Frank Martin (a musical "anatomy of melancholy")
Herbert Howells
Kenneth Leighton