The Witcher 2

Apparently GAME are doing a trade selected 2 games in get Witcher 2 for 99p offer, some of the titles on the list can be obtained relatively cheap.

Examples halo anniversary/assassins creed rev etc.

Green man gaming are doing the pc version for £25

On the PC one could just buy an older version of the game, like this one from play for £12:
http://www.play.com/Games/PC/4-/25404010/The-Witcher-2-Assassins-Of-Kings-Version-2-0/Product.html

And then download the FREE patch to upgrade it to the Enhanced Edition:
http://en.thewitcher.com/enhancededition/