C#, obviously. It's the only modern language that provides ALL of the following:
1) Static and dynamic typing
2) OOP and functional paradigms
3) Multi-platform via single framework: WP, Android, iOS, Mac, PC, Xbox, PS4, Linux etc.
4) Two super-powerful IDE-integrated static analysis tools to choose from: ReSharper and Roslyn
5) Mature workflows for developing Web, mobile, enterprise apps and games.
6) High performance on WP and desktop, reasonable elsewhere.