Definitely "Rescue on Fractalus!", back from the Atari 8-Bit era. There's an "alpha" version for PC which is OK, but I would lay down hard cash for the chance to play it on a more modern (ahem!) system; to play it on my Miggy would be a dream come true.
Might be tricky; I'm no mathematician but the original used fractal-generating routines to product its' pseudo 3D effect (on an 8-BIT MACHINE!); also ranks up there for providing some tense and scary moments when waiting for the pilots to run up to the door...
