If there is one collectible NES game that has legendary I.P. conflict written all over it, then it has to be Tengen Tetris. Atari-controlled company Tengen, you see, despite apparently only having the rights for the computer versions of Tetris, went on and produced an excellent port of the game for Nintendo's 8-bit console. But, with Nintendo having already acquired the Tetris rights on consoles (only) and producing -an inferior, though legally superior- version of the game, Tengen was forced to withdraw and remove its cartridges from shops worldwide. Thus Tengen's Tetris became a rarity. A rarity you can now grab for a modest price by following this Tengen Tetris NES eBay link. Seller ships worldwide.