I will leave out databases, other declarative schemas, language super- or subsets or markup languages.
I wrote applications, programms in all of them. C is the language I learned in school. And If I take the things I helped my girlfriend with when she was studying technical mathematics in theory I could add C++ ... but than I would have to add Ruby as well for starting to write a Redmine plugin.
Go is one where I did not write a professional application with, but just was writing algorithms, a lexer, a http server, ....
I am thinking of adding ReasonML since it's syntax is related to Rust.
And I have elixir and pony on my 'next' list. But currently Rust is taking a lot of time with the experiments, hacking groups, meetups and deeper understanding.