Spray's Json parser vs. Argonaut's in a head-to-head battle to the death.
Using the magnet pattern to get around a limitation with Scala's overloading implementation.
This is a pretty neat use of Scala's implicits to pimp Akka's messaging system in order to add a lot of meta-protocol information about who's sending what, to whom they're sending it, and adding some more information along the way.
How I moved from WordPress to Github Pages, along with Jekyll and all the good stuff.
A video on how I code Scala with Vim, along with a lot of explanation as to how it gets done.