This launch trailer gives you a good look at Infinity Blade, the role-playing game for iPhone 4 (and iPad and iPod Touch) being built by Chair Entertainment and Epic Games, whose Unreal Engine makes the whole thing go.
Chair has said they think they've got the potential "best looking handheld game ever made," and it's hard to argue with visuals like that. This is a trailer viewed on the PC, but the iPhone 4's Retina display should do it plenty of justice. And the swipe controls shown look like they're suited to both device and game.
Color me intrigued. A solid RPG on the iPhone? I bet I could kill one hell of a long cross-country flight with that thing.
Clarification: This game will be playable on the iPhone 4, iPhone 3GS, iPad, iPod Touch, and the iTouch 4.