World Karate Championship, Ballblazer and Archon (default game would probably be too long but there are ways to shorten it, it is a classic game that I think should be played somehow) for the Atari 8 bit are great head to head games. Combat, Kaboom, Pele's Soccer for the 2600 are great, I think Kaboom even has a mode where one player can be the mad bomber and the other player has to catch the bombs, that might have been only in the 8 bit version but it is great fun. Those are off the top of my head, I will try to think of some more.