I don't think Rhino's being used much in production (correct me if I'm wrong) perhaps because of slow execute times, but the far racier Nashorn is likely to kick out any lingering use of languages used for JVM scripty stuff, e.g. Groovy, Xtend, Beanshell.
Clojure - concurrency (immutable by default), macros (lisp-style)
Scala - object/functional fusion, lazy evaluation
Ruby dialect (JRuby or Groovy) - "methodMissing" meta-object protocol
Java - low-level OOP (but functional lambdas and lazy streams coming in Java 8)
COMING SOON: Javascript (Rhino or Nashorn) - functional with prototype-style OOP