This week's Amazon Ad lists two of the biggest titles of last year BioShock and Assassin's Creed each for $39.99.
Also avialable is Enemy Territory: Quake Wars for $19.99 and an online only deal that will net you two games priced $19.99 each for $30.
Some of the titles offered in that deal include COD 2, Viva Pinata, LEGO: Star Wars II, Red Steel and a ton of PS2 titles. The weekly ad deals last until next Saturday but the online offer has no stated ending date.
If you want cash in on the hidden gems though, I would jump on it ASAP.
Source: BestBuy