optional is a command line option parser and library.
YOU WRITE:
object MyAwesomeCommandLineTool extends optional.Application {
  // for instance...
  def main(count: Option[Int], file: Option[java.io.File], arg1: String) {
    [...]
  }
}
THEN YOU DO:
  scala MyAwesomeCommandLineTool --count 5 quux
AND YOUR MAIN METHOD WILL BE INVOKED SUCH THAT:
  count = Some(5)
  file = None
  arg1 = quux
  
See the example programs for many more features.
HOW IT WORKS:
  Reflection, man.
CREDITS:
  Idea and prototype implementation: DRMacIver.
   Fleshing out and awesomification: paulp.