The Game: You’re a lone attack helicopter jockey in unfriendly desert territory, trying to stop a seemingly endless attacking fleet of enemy jets from bombing a convoy on the ground. (Activision, 1982)
Memories: Maybe the best example ever of Activision stealing Atari’s thunder right out from under it, Chopper Command is essentially the same game as Defender, with the singular exception that the enemy is bombing the ground-dwellers instead of trying to abduct them.
Chopper Command is much more visually pleasing in and of itself, with the added bonus that Activision’s crack squad of Atari vets also managed to once again do away with the annoying flickering that plagued Atari’s own releases. But other than that, the lateral scrolling, the “radar screen” showing the entire playing field and not just the 
portion that you happen to inhabit, and other elements of the game seem very familiar.
Atari, of course, had gone through the trouble of licensing Defender, which turned out to be blocky and flickery in cartridge form – i.e. what people expected from the 2600.