title: What are all the uses of an underscore in Scala?
body: <p>I've taken a look at <a href="http://www.scala-lang.org/poll" rel="noreferrer">the list</a> of surveys taken on <a href="http://www.scala-lang.org/" rel="noreferrer">scala-lang.org</a> and noticed a curious question: "<a href="http://www.scala-lang.org/node/5496" rel="noreferrer">Can you name all the uses of “_”?</a>". Can you? If yes, please do so here. Explanatory examples are appreciated.</p>