I recently wrote up a "cheat sheet" for Scala.
You can download a .pdf copy of the file here.
My office is coming together nicely thanks to "decorations" as such.
https://alvinalexander.com/downloads/scala/Scala-Cheat-Sheet-devdaily.pdf (75% “copied” from his material)
http://blog.originate.com/blog/2014/06/15/idiomatic-scala-your-options-do-not-match/ (see: The Ultimate Scala Option Cheat Sheet)