Cex are selling the epic Sci-fi shooter KillZone 2 for the measley sum of just £6. Still thousands of players online, trophies and great graphics and a decent storyline make this a bargain. It was priced at £6 a few months back but only lasted a week before the price rose back up, so why it's only £6 grab it while it's hot.
This price includes delivery from the online site, but personally I'd check the stock quantity at your local store on the right hand side of the page, and if it's in stock buy it from your local store. That way you can make sure you get a perfect copy.
I posted this a couple of months back, but Cex since put the price back up. However, it's dropped again, so grab it while you can.