That all depends on the application, I guess ;-) Usually I end-up using Python for smaller things that aren't mission-critical or need maximum performance, C++

That all depends on the application, I guess ;-) Usually I end-up using Python for smaller things that aren't mission-critical or need maximum performance, C++ for almost everything else, and Objective-C for OS X/iOS stuff. Maybe Java for things where both performance, safety and ease-of-development/maintenance matter (the latter would be mostly for other people who would have to work on the same projection who are less skilled in C++, as I'm not at all a fan of the language myself, but I recognize it has some properties that make it a suitable choice for many kinds of applications ;-). I don't have enough experience with any other programming languages that can be deployed easily across Linux and OS X, so I can't comment on those. Rust seems to have some good ideas so I may want to learn more about it in the future. If I wanted to write something for Windows platforms I'd most likely gravitate towards C#, from what I know about the language it appears to have all the good things of Java without its downsides.