Self: The power of simplicity. This is another "everything is an object" approach, but more so than even Smalltalk (where you had classes, and then objects, and then classes were objects, but then the objects that were classes had to be instances of some class, and it eventually has to be circular somewhere). I've never seen a prototype-based language before, even though I've read about them a bunch.
Been playing with GNU R lately. I wish I knew more about statistics...