Walmart seems to be issuing new $5 Reservation cards all the time. They are available in Electronics, on an endcap display and/or locked up in the videogame section - - and some stores also have a nifty cardboard POP display just for them. Identified as VIP Pre-Order Program Reservation Cards, they are intended to reserve a copy of a soon-to-be-released game, but can also be used for purchases throughout the store. The cards are typically removed from the shelves after the game has been released, but not always; the cards can still be activated and used. Walmart has an on-line site where purchasers can unlock additional bonus content (as noted on the plastic backboard), which shows a variety of cards already issued (including, alas, 6 cards I missed): http://zreward.com/categories/1/products
For some reason, they appear on the register display (and your receipt) as phone cards during activation, but I have used them to purchase food and supplies at Walmart. They do not work at Walmart gas pumps. Once in a while a register will display that the gift card I'm using is a phone card and won't decrement the value on my card, but if the associate tries again, the transaction will go through.