And of anyone has the 15 off 100 coupons from a couple of weeks ago, most of them they're working at checkout (1 out of 4 didn't work for me).
Basically, the 2 for $20 is on all games $19.99 & under except XBox & XBox 360. The only thing you have to make sure of is you have an even multiple of games in the same category tree (PS3/PS2, PSP, Wii/GameCube, DS/GBA). For example, if you have 1 PSP and 1 DS, it won't work but. There are also a couple of games they have at $29.99 and $39.99 that are coming up 2 for $20 but nothing great (Ape Escape 3, Neopets and Genji are the ones I recall).