Gamestop UK will allow you to buy Call of Duty: MW3 from them for £0.99, around $1.35USD, all you have to do is trade in your copy of Battlefield 3.
This is a pretty good deal if you are a CoD fan.
Simply purchase Battlefield 3 before midnight on October 27th and then purchase Modern Warfare 3 before midnight on November 7th. Gamestop will refund you for your purchase of Battlefield 3 except for the £0.99/$1.35.
You will need to send Battlefield 3 back to Gamestop before the 18th of November to be eligible.
That works out to be three weeks playtime before sending it back for CoD:MW3.
Modern Warfare 3 will cost £41.97 at GameStop while Battlefield 3 costs £36.97.
Activision obviously has this accounted for in their marketing plans and the slightly higher price point.
If you are unsure of which of the latest multi-player shooters you intend to get, well, this could be a great way to try them both.
This is a new step in the war for players, a fairly dirty one too. Sure, this deal has Gamestops name attached to it, not Activisions, but you would expect they are involved.
We can't really name any other titles that have flat out offered you a trade in on a competitors game, that just came out!
Personally, the constant versions of CoD and Battlefield that are released every 6 months are starting to get a little bit old. Certainly won't be buying Call of Duty 4 for PC, Xbox or PS. The map packs for Call of Duty are really uninteresting too.
Now if they offered me a trade in for Leisure Suit Larry 1-7 (the originals), I'd be there in a second.
Not a fan of this type of marketing myself, it feels very like big business not actually looking to help the gaming industry out.