Pepsi invaders - One of the first and rarest advergames
Pepsi Invaders was one of earlier advergames that was developed for Atari 2600 platform. Game was commissioned by Coca-Cola and developed by Atari. Because Coca-Cola published it, you can sometimes find it under name Coke wins. Advergame dates back to 1983, and it one of the first advergames.
Game is a modification of original Space Invaders, which you surely know of. Because original game had six aliens rows, and word Pepsi only 5 letters, they left one alien row. They also changed limited lives to unlimited, but shortened time form unlimited to a three-minute time limit. What is also interesting, Atari used hack of original ROM cartridge of Space Invaders. Compared to original Space invaders, spaceshuttle is less wide, thus making avoiding hostile projectiles easier. Although time limitation makes shooting accuracy more important so it balances gameplay.
One more interesting thing about Pepsi Invaders is the game rarity. They only gave 125 copies of this game to sales executives attending 1983 sales convention, so this game is really rare. In the year 2010 one of collectors bought a copy of Pepsi invaders on eBay for $2,125.