EDIT: According to TechnoKilla it works on some other games too, and confirmed, works with some hard copies and pre-orders too!!
For a limited time you can get Battlefield: Bad Company 2 for $20!
PC Games : Computer Games - EA Games
Click on Download
then click Checkout
Put in the promotional code PAXEAST842 <--- Make sure that it's in ALL CAPS! or it won't work!
Then click Apply and your Subtotal should come up to $19.95!