Though Super Mario Galaxy 2 (Wii) isn't due until May 23 and Halo: Reach (Xbox 360) isn't hitting until this fall, retailer Walmart.com has joined the pre-order arms race, offering up an immediate $20 e-gift card in exchange for pre-orders of either game.

Those that pre-order will be able to use their newfound online store credit immediately, which is nice. Not so nice is the part where the "Estimated Arrival Date" suggests the games won't hit your doorstep until a few days after their respective release dates.

Still, getting $20 back--even if it's in the form of store credit--is nothing to sneeze at, especially as that represents about a third of each game's cost. But whatever you chose, make your decision soon, as we're told this offer is only good for a limited time.