I'll probably think of more soon, but for now I'll go with the first two names I thought of when I saw the thread title:
Robert De Niro and Charles Grodin in the very underrated Midnight Run. Anybody who has never seen this should seek it out. They work off each other very well. I've seen it countless times and they both still make me chuckle. This proves that De Niro can do comedy. He hasn't shown it very much since however.