For FIRST robotics in particular, Java and LabView are the most commonly used languages because they are the two for which a robust library is maintained by Worcester Polytechnic Institute for use in the competition.

But I have long been of the opinion that both languages are kind of an ill fit for the application. Python is making some headway and I think it might be a better fit; It has some advantages on legibility, it has an optional static typing system, and it does support coroutines.