I want a Karate Champ. It was the first arcade game I ever got good at (when I was 9 in '84), and I still remember all the joystick combinations for the moves.
These days though, I'd mostly have it for nostalgic purposes, because as far as gameplay goes, it is no SFII by any stretch of the imagination. You can beat all the levels the first time around with just one move (kneeling reverse punch for [usually] a full point).
Playing against a human opponent is more fun (with the VS. version), but even then, if you're both good at the game, most matches will be a standoff, with both players going on the defensive (because there is no way to initiate a strong offense in the game). Defensive play is inherently stronger than offensive play in this game due to the way it was designed. Because of this imbalance, the game designers had to make the computer opponent get faster rather than just playing better; in order to increase difficulty as you progress in the game. By the time you get back to level 1, the CPU opponent is practically sprinting across the screen; while your playable character still moves with the same lethargy as always.
SFII for example, is far more balanced in this respect.