I only find my MTB superior on the one day a week I load up the panniers or during the winter months or when I'm up for a trail ride home. Otherwise the roadie's more fun.

Back to the MTB subject, here are some of my favorites:

Trek 950 - 990
Diamond Back Apex
MB-3 or less
GT Karakoram, Avalanche or Zaskar
Specialized Stumpjumper
Bianchi Grizzly (gotta go back to 92 or so for a stock rigid, though)
The two in my sig,

etc, etc.