The The Witcher 2: Assassins of Kings just got upgraded to version 2.0. To celebrate GOG has marked the game down to $29.99. You can pick it up for only $23.99 at Amazon (US Only), but buying from GOG supports the devs directly. Also some people like to keep their games in the same place.
The Witcher 2 has an 87/100 metascore.
This special sale lasts until October 6.
Read more about the Witcher 2 version 2.0 deal at GOG.
EDIT: Looks like Steam has it for $29.99 also.