Shares of GameStop Corp. plunged almost 19 percent after a profit outlook from the video game retailer came in below expectations for the crucial holiday period, though sales were strong. GameStop forecasts fourth-quarter earnings of $1.85 to $1.95 per share, down from its earlier outlook of $1.97 to $2.14. Analysts had predicted earnings of $2.14. GameStop said sales at stores open at least a year increased 10.2 percent for the nine-week holiday season. That topped the 4.4 percent rise Wall Street had expected.