My first game in the oldest (silver) series is Judge. It's from 1980, and it involves two guys whacking each other on the head with a hammer.
This is actually one of the first Game & Watch games Nintendo ever released, after Ball, Flagman, Vermin and Fire.
Judge can be played with both one and two players, and I quite like it. You have to quickly respond to the numbers the two guys hold up and then perfectly time your dodge or hit.