Can't believe I haven't seen this mentioned here, but Impossible Mission DS has a temporary $10 price drop down to $9.99 until 12/02. Already back-ordered online, but I verified the price is good in-store and grabbed an extra for my brother while I was there.
http://www.gamestop.com/product.asp?product_id=180683
http://www.gamestop.com/product.asp?product_id=180683