My favorite Karnov moment was in Bad Dudes. After killing him as the boss of the first level, the ghost of Karnov returns on the train level -- with a vengeance! God I love that game.
Those fat jokes in Fighter's History Dynamite always crack me up.
That's another game I'd like to spend some time playing. I've always wanted to be able to beat Karnov, or at least get to the last guy. Usually I don't make it out of level 2 though.
My fondest memory of the NES version of Karnov is that if you had a controller plugged into the second port, you could commit suicide by pressing... the "A" button, I think? Being a one player game and all, this came in handy when I was anxious for my turn.