I don't really have a single favorite a language, if I am able to choose freely it depends on the task.

• C++ for natively compiled programs and C interoperability, I like the types from the STL and templates.
• Clojure is IMO great for data-oriented programs, I really like the immutability and it being a lisp. The java interop and the ability to compile to JavaScript with clojurescript can also be useful.
• Julia for smaller (mostly numerical) programs that should be fast at runtime. The type system is great in being optional, but strong and significantly improving performance when types annotations are used.
• Fennel (or Lua) is definitely my favorite Language for embedding into larger programs and scripting. Fennel has the advantage of being a lisp and cleanly compiling to lua.
• brainf*ck is great as a simple language to have fun and enjoy programming