Both Earthworm Jim 3D and MDK are really fun parodies/platformers on 3rd person shooters. I played MDK2 not so long ago, and it's been a while since I played EWJ, but I remember it was a really fun game, however! Very hard also because there was no saving function.
As for Descent, I played 1 and 2, and they were really cool, but heck! The headache you would receive from all that spinning 360 degrees and anti-gravity claustrophobic feeling of the game were a bit of a minus. Oh, well. I guess I shouldn't be playing FPSs if I get dizzy so easily.