Rubinius
In my view, Ruby isn’t finished. It’s a great substrate for Rails, it’s immensely useful for building all sorts of things, but it’s not fast enough. I agree with Avi Bryant’s argument that a language isn’t finished until it’s fast enough to extend itself. Frankly, none of the language enhancements proposed for Ruby 2.0 make my heart go pitter-patter. But give me a Ruby with performance as good as a really good Smalltalk VM, and the space of things for which you need statically-typed languages shrinks to a really uninteresting size.