Amazon. I had a buncha credit with them, so by using their promotional credits with some new release games I basically made my own 'coupon train' and managed to get 5 releases at launch for about $160-180 in credit.
I got Uncharted 3, Battlefield 3, Arkham City, Lord Of The Rings: War In The North and Saint's Row 3 all at release thanks to $10-20 credits that the prior game in the chain had.
That reminds me, I have a $10 promo credit sitting on my account I better use up.