Depends on the purpose. I write mainly Python at home and at work, sometimes create small to medium sized Bash scripts, use PHP for my personal websites and most web projects, sometimes a few lines of Javascript (command line, I mean, not as part of html/css/js), sometimes some Java at work, LaTeX macros for documents... If speed is paramount (rarely) I'll also write C/C++ or maybe Go, but those are not my forte.

So it really depends on the purpose of the project, who else works on it, what it needs to integrate with, etc.

Thinking about what I use, C# didn't even come to mind. I only used it when required in school or when interning in companies that run Windows. I've written some C# on Linux at home but it's not much more than my experiments with Brainfuck were...