Rust / Various notes on Rust.
These days, Rust is hands down my favorite programming language. I think traits are a vast improvement over C++'s flavor of OOP and polymorphism; I love Cargo, the included build system and package manager; and overall I just find it a much more enjoyable language to use, more so than even Python. It was pretty difficult to get used to, but the lessons I've learned along the way have been invaluable.