F#. It is well supported and the tooling works out of the box. Lots of data analysis tools, winforms for graphs, REPL...etc. The doc could be better though and there is no real beginner tutorials. Everything assumes intermediate to advanced C# knowledge.
Scala -- great online learning resources (Coursera series), good integration with Eclipse, unique and convenient "worksheet" interface and repl, and significant benefits when working developing big data applications with Spark.