#20 - CombatReleased 1977 for Atari 2600
This is obviously a simple two player game, but surprisingly it comes with a great deal of variety. My brother and I spent a lot of time playing this game. It's a multi-directional shooter and exclusively two-player, so you had to have a friend or sibling with you to play it.
There were three vehicle types:
Tank - One on one action where you accumulated points for how many times you shot your opponent until the timer reached zero. Depending on what mode you selected pre-game, there were straight shots, guided missiles that you could roughly guide with the joystick after firing, and ricochet shots that you could bounce off walls to hit your opponent. There was also a mode for invisible tanks that only appeared for a few seconds after firing a shot. The combat map could be selected from an empty field, a simple maze, or a more complex maze.
Biplane - You could choose to play one on one, two on two (the planes moved in tandem), or three on one in which one person controlled three planes in tandem while another person controlled a large bomber plane. No maps in this mode, but there were two clouds on the screen and you could fly into the clouds so your opponent couldn't see you for a few seconds.
Jet - More maneuverable and faster than the biplanes, but this mode only had one on one, two on two, or three on three.
It was remarkable how this game got our competitive juices flowing. Hitting that perfect bounce shot to score a point on the tanks was an incredible feeling.