Zale and McCallum are the two obvious ones that that spring to mind immediatly. I always thought Hopkin's single shot KO of Hoya was a thing of beauty.
Fitzsimmons more famous for probably the most famous body punch at heavyweight.....Corbett, or any weight
Tiger was a great body puncher - when he remembered to actually target to the body. Unfortunately, he had a bad habit of headhunting and thus foresaking what was really one of his best assets.
How about Nunn? It was one weight up at super middle, but his body work against Crawford Ashley is some of the best you'll ever see.