I think there have been some one-off Wal-Mart sponsorships in the Cup Series (like in conjuction with another sponsor). I know there is a guy racing at the Toyota All-Star Showdown that has sponsorship from Pepsi and Wal-Mart and I think I have seen some drivers in the past with Wal-Mart on the side of their cars at Irwindale for some of the bigger races.