Shopto pretty much came from nowhere to be one of my favorite video game retailers. They have pretty great prices for the most part, and they tend to get you your games pretty fast.
They have just made a change in policy regarding pre-orders, which is a bold move, and I would love to see other retailers follow suit.
If you preorder a game by 12pm two days before the official release date, and they fail to get the game to you by the release date, you will get £3 store credit.
Terms and conditions apply, see here for details.
Cheers to chanticleer for the tip off.
Dark Sector, Xbox 360 - £4.91 delivered
It's been around this price in a few places for a while, but this is the cheapest price at the moment.
Update: Price has gone up gone up now at Asda, but play.com still have it for a fiver.