Infinity Blade II, Traktor DJ, Sword and Sworcery, Day One available for free on the Apple App Store
The apps includes Infinity Blade II which usually costs $7 can now be downloaded for free on the App Store, others include Tiny Wings (and Tiny Wings HD for iPad), Traktor DJ (normally $20), Superbrothers: Sword & Sorcery EP, Traktor DJ, Where's my water, Badland.
The apps listed above are by no means the only premium apps acceptable for free,
Tiny Wings HD
Superbrothers: Sword & Sworcery EP
Infinity Blade II
Where's my water?