Combat was designed by Atari, Inc. and first released for the Atari 2600 in 1977 and was the pack-in game for the system until 1982 (meaning: you got a Combat cartridge with the console, upon purchase).
It was one of the first home video games I ever played (probably the same for millions of others) and it enthralled me. Yes, Combat is very simple by today’s standards, but in 1977 it was a revelation.
As a two-player game it is up there with the best of all time. Tanks, jets, biplanes – each player took control of one of these and chased each other around a single screen, in order to blast them with bullets. With tanks you are placed in a maze; with planes you fight it out in a cloudy sky (look at those clouds…). Various skill settings allowed you to choose things like bouncing bullets, or more planes, or different mazes. In total there are 27 different types of screens in Combat.
Combat has also been re-made numerous times for different systems, and also has a sequel, Combat Two, which remained unreleased until 2001, when somebody put the completed prototype onto a limited number of actual cartridges.
More: Combat on Wikipedia