Flat UI color palette as NS/UIColor objects (in Swift).
Functional programming tools and experiments (in Swift). Lots of functions.
Regular expression class (in Swift). Wraps NSRegularExpression.
NS_OPTIONS for Swift (type-checked bitmask container). Basically an easier-to-implement RawOptionSet.
Basic data structures (LinkedList, Queue, Stack, OrderedDictionary, OrderedSet).
Scene loop timer for keeping nodes in your scene graph in sync (works with SpriteKit, etc.)