Wal-Mart Stores Inc will allow U.S. shoppers to trade in used videogames for anything from groceries to gadgets, a move that could dent the profit of GameStop Corp, the largest dealer of used videogames. GameStop shares fell as much as 6 percent in morning trading, making it one of the top percentage losers on the New York Stock Exchange. Wal-Mart said on Tuesday its trade-in service will accept games for popular consoles like the Sony Corp’s PlayStation3 and Microsoft Corp’s Xbox 360, and customers can in return buy anything at Walmart and Sam’s Club. “Gaming continues to be an important business for us and we’re actively taking aim at the $2 billion pre-owned videogame opportunity,” Duncan Mac Naughton, chief merchandising and marketing officer for Walmart U.S., said in a statement.