For today only, Gamestop is extending a buy one get one 50% off promo to all pre-owned iPod, iPhone and iPads.
Update: Deal appears to be live until 12/15/12. Discount will show in your shopping cart once you add two applicable devices.
B1G1-HALF OFF CONSUMER ELECTRONICS - Buy 1 Get 1 50% off on Pre-owned Electronics! Offer valid on instock items only while supplies last. 50% off applies to items of equal or lessor value. Other restrictions may apply. Expires 12/15/12 – iPad(R) 2 16GB WiFi (Scratch & Scuff)
Some examples of available deals include: