In reply to broken spectre:
Just found a "buddy films list" on Wiki and it makes interesting reading.
My other nomination after Midnight Run would be Cutter's Way, one of the most underrated films ever made.
Admittedly it features a woman disturbing the buddy relationship (as shagging your best friend's girl is wont to do)( and her performance in this film should have garnered her some major awards) but the two blokes and their troubled relationship is a winner in every sense.
Contains some of the most haunting movie music I've ever heard and an absolutely hilarious drunk driving scene