Vim + Eclim + Scala
WARNING! Do not install anything from update sites before installing Eclim! This is because Eclim determines available project natures (android, scala, etc) by trying to discover them at install time. If they are installed on a per-user basis, it won't find them. If you're installing Eclim for use with an existing Eclipse install
You're also better off not to install any plugins via your package manager. Eclim will give you the option to install plugins associated with each project nature from its install wizard.
Install Eclipse Luna. On Arch Linux, it's available in extra.
pacman -Sy eclipse