pure: A recondite and tasty language by Alber Gräf, that I intended to learn because it looked handy and elegant.
Pure is a modern-style functional programming language based on term rewriting. It offers equational definitions with pattern matching, full symbolic rewriting capabilities, dynamic typing, eager and lazy evaluation, lexical closures, built-in list and matrix support and an easy-to-use C interface. The interpreter uses LLVM as a backend to JIT-compile Pure programs to fast native code.[…] It also integrates nicely with a number of other computing environments, most notably Faust, PureData, Octave, Reduce and TeXmacs. A fairly extensive collection of addon modules is available, which makes Pure usable as a compiled scripting language for a variety of purposes.
I won't learn it, though; If I do learn an extra language it will be julia, clojure, or perhaps scala, purely because they have larger communities. This is sufficient reason.