Infinity Blade, the action RPG from Chair Entertainment and Epic Games, is Apple's “App of the Week” and is thus free for iPhone and iPad until the 21st of February. Not only is the game absolutely stunning, a poster child for what these devices are capable of when it comes to high-quality games, but it's fun to play too. If you haven't tried it out, now's the time, since you won't lose anything even if you hate it.
First released in 2010, Infinity Blade was the first iOS game to run on the Unreal Engine 3. It looks damned impressive, with detailed environments and lighting effects. Though you don't have full control over where your character goes, you can look around you to pick up items, and it feels smooth.
As far as how the game plays, you control a male hero seeking to avenge his father, killed with the titular Infinity Blade. You move from enemy to enemy, (hopefully) wiping out each in turn as you make it to the top of the main big bad guy's castle. It's fairly standard stuff, but then the story is not the primary focus here. Instead, enjoy the pretty surroundings and the battles, which involve using the touch controls to block, dodge, and swipe at your opponents with your sword.
If you really like Infinity Blade, Infinity Blade 2 is even better (though it does currently cost money). Around this time last year, the franchise had already made over $30 million, so it's definitely worth a look even if just to find out what all the fuss is about.
