SceneKit. A framework that's existed on OSX since 2012, it's a relatively new framework on iOS. Since the very beginning, developers have pined for a framework like this on iOS. Before SceneKit, to build even a simple game you had to build on a third party framework that was often messy and hard to use. With the introduction of SceneKit, it's now easy to get something up and running.
Let's get started then, shall we? I won't go into very much code this time around because even writing an introduction would require more time than I have, but I'll discuss a bit about the technologies behind it.
In Xcode, select
New -> iOS -> Application -> Game. Select your language of choice, then go ahead and hit next.
Right now, you don't even have to touch one line of code. Go ahead and hit run, and you'll see a rotating airplane. Gestures are already enabled by default, so you can pinch, rotate, and pan the plane.
The thing with SceneKit is that it is so easy to use it. Comparable frameworks such as OpenGL usually takes forever to make something even remotely similar to what SceneKit can accomplish in only 100 lines. Another plus of SceneKit is that it can be coupled with the new Metal APIs also introduced in iOS 8, enabling some incredible feats of graphical computing.
Apple actually has a pretty cool demo game built with SceneKit. It's called Bananas, and you can find it here. By examining the code of Bananas you can actually learn a lot of things SceneKit has to offer. Have fun with SceneKit, and remember to refresh your scenes!