Dead Rising 2 and the spinoff Dead Rising 2: Off the Record, available for the low price of just $12.99 a piece. Dead Rising 2 OTR is on PSN for the same price as part of the Halloween sale. That's a huge saving on zombie killings: One of the game's achievements asks you to kill 72,000 zombies, so if you finish that achievement, you'll only have paid 1/50th (rounded off, of course) of a cent per kill! It's rare you find zombie killing that cheap these days, especially in this economy.
Plus, if you've already played Dead Rising 2, this is your chance to play that Off the Record version, which places the first Dead Rising's Frank West in the protagonist's chair. Being that it's the deal of the week, the offer lasts no more than seven days from now (and probably less, depending on when you're reading this), so if you want to take Capcom up on it, grab away.