Also interesting (historically) is 'Rescue on Fractalus'. Not just for its cheesy name, but also due to its reliance on fractals to draw 3D mountain sceneries:
Rescue on Fractalus had one of the most genuinely terrifying game moments of my 'career'. I won't spoil it here, but you can probably guess what it was from the wikipedia page.
I love NovaLogic's games and their voxel engine, don't they own several patents on voxel engine based games? I think I remember that coming up in a discussion a few years back on why we haven't seen more voxel games prior to this recent slew(besides hardware liking polygons more).
(To add to the confusion, this particular game, Ace of Spades, actually is voxel-rendered.)
It is however thought that John Carmack's next engine after the Rage engine may include honest-to-goodness voxel rendering: http://en.wikipedia.org/wiki/Id_Tech_6
Historically, Carmack has had quite a lot of influence on both the hardware and API vendors, so it will be interesting to see if he can spearhead more mainstream movement towards sparse voxel octree rendering: http://youtu.be/THaam5mwIR8