NEW YORK ( TheStreet) - GameStop's ( GME) stock is tanking after Wal-Mart ( WMT) announced it is cutting prices on video games. On Wednesday, the discount behemoth said it is offering a 15% to 25% discount on top 25 video games, including Mario & Sonic at the Winter Olympics and Madden 2010. It will also reward shoppers who purchase a Nintendo Wii console with a $50 gift card. As a result, GameStop is tumbling 8.5% to $21.83 in morning trading. Shares of Wal-Mart are flat at $54.74. While no hard data is available, investors feared sales of video games were not as strong as expected over the holiday weekend. -- Reported by Jeanine Poggi in New York Follow TheStreet.com on Twitter and become a fan on Facebook.