Zavvi.co.uk have dropped the price of three popular xbox 360 games this weekend only as follows (links added to relevant pages):
Kane and Lynch 2 £17.95
Crackdown 2 £17.95
Alan Wake £15.95

Next best prices found online for the above games are as follows:

Kane and Lynch 2 £26.95 (Base.com)
Crackdown 2 £20.38 (Amazon)
Alan Wake £17.93 (Amazon)