Brandon Withrow (and others from the AirBnB team) with an ambitious library to take After Effects animations exported with bodymovin to play directly inside a UIView in your app. The API is ridiculously easy and it even supports custom view controller transitions. This looks amazing.
Swift is a great language for building command line tools, but there's more to a command line tool than just the ability to run from Terminal. What about commands, and arguments? Or flags that only apply to certain commands? It can be tough to make the "UI" for a command line tool follow conventions and make sense to users. Guaka should come in handy if you're building anything more than the most trivial tool.
This quick tip by Erica Sadun is worth knowing. Not something you'll need every day but better than having to tag every value in your enum.
However, remember that just because you can, doesn't always mean that you should! 😀