I'm a big fan of B minor. A lot of my favourite music I have later found out is in that key. Tchaikovsky used in for two of his symphonies, including his longest, Manfred. It also features prominently in Swan Lake. Other great works in the key include Shostakovich's 6th Symphony, Gliére's 3rd (Il'ya Muromets) and Paderewski's only symphony (Polonia), the latter two of these are both epic works of over 70 minutes' duration.

Arnold Bax's 2nd and 4th Symphonies both call for organ, No. 2 featuring a deep pedal C in the slow movement and the finale. The 4th has it at the beginning of the symphony, at the end of the first movement (my favourite moment of Bax music), and the last few minutes of the finale.