Gibson Guitar Corp. today sued Wal-Mart Stores Inc. and five other major retailers that sell the Activision "Guitar Hero" game, claiming it violates a patent it holds. A federal lawsuit filed Monday claims Wal-Mart, Target Corp., Kmart, Amazon.com, GameStop Corp. and Toys "R" Us should stop selling the game.Gibson has already tried to stop video game publisher Activision Inc. from selling all versions of the game, claiming it too closely matches a musical virtual-reality patent from 1999.