PlayStation Plus members can grab the PSone classic Twisted Metal 2 and the not-so-classic Tomb Raider: The Last Revelation for 50% this month, along with a few other specialty priced items. The only available free game for Plus users this month is the PS Mini, Vector TD.
In sale news for all users, the addictive card game Uno is available for $0.99 for a limited time, the MAG Escalation Mission Pack is $7.99, and (my PSP holiday pick) Metal Gear Solid: Peace Walker has permanently dropped to $29.99.
For a complete listing of this week's PSN offerings, check the official PlayStation Blog.
So yeah.... dead nation is amazing so far... not you're typical top down zombie shooter at all.
need to play a bit more to be able to explain further though...