F Sharp

It's main strength doesn't lie in any isolated language features that C# might appropriate, but in the fact that it's a functional-first language. The language itself is designed from the ground up to encourage a programming style that is more logical, concise and modular than OOP. F# code has been proven time and time again to be far more compact and refactorable than C# code on average, and an order of magnitudes less error-prone.

F# is the kind of language that doesn't let you get away with sloppy coding, for better or worse. Not as efficient for quick prototyping as a language like Python, say, especially if you're way more familiar with the OOP paradigm, as most programmers today still are, but if you want reliability and maintainability with access to a vast library, there are few better options (only Scala comes close, I'd argue). This reliability and innate security is one of the reasons why it's relatively popular in the financial sector.