Pepsi Invaders (aka Coke Wins) is an ultra-rare Atari 2600 cartridge that was given to Coca-Cola employees in 1983. Only 125 copies of the game were ever produced, without labels or boxes. Needless to say, this game scores a full 10 on the AtariAge.com rareness meter. A copy of the game surfaced and was recently sold on eBay for $1,825. That's a spendy Space Invaders clone.
Pepsi Invaders is a simple Space Invaders clone. The game was developed by Atari under a commission from Coca-Cola. It was given as a gift to attendees at a sales convention, hence the low production number. Developed by Atari programmer Christopher Omarzu, the actual game displays "Coke Wins" as the title on-screen, although the official title is Pepsi Invaders.
Game collectors can be sure that their cartridge is legitimate by checking the hardware: In spite of the low production run, the game was burned onto a regular Atari ROM chip, as opposed to the EPROM chips that were usually used in such small batches of a game.
You can check out the archive of the eBay auction (which is now over) at this link.