When I think of a classical instrument, I think cello - specifically this piece Shadow of Doubt by Yoko Kanno, where it has such a brooding tone and power.

Being a synthesizer nerd, I like those most, but they have such varied tones among them and even on the same synth; 4x Atlantis by Aphex Twin probably captures one of the tones I most love, and the entire "Orphans" piece hits much of the range.