SpriteKit
Apple's built-in 2D game framework, which arrived with iOS 7 in 2013 and made most third-party engines unnecessary for anyone just making an iPhone game.
A SpriteKit scene is a tree of nodes (SKNode) — sprites, labels, particle emitters — rendered with automatic batching. Movement and effects are described as SKAction sequences rather than worked out by hand in your own game loop, and physics and collision detection come built in. Xcode also packs images into texture atlases automatically.
The framework was Apple's answer to developers otherwise reaching for Cocos2d, whose API it resembles quite a bit. The price is lock-in: SpriteKit exists only on Apple platforms, so a game bound for Android has to be rewritten.