Python. C

Haskell: distilling ad hoc solutions into mathematical gems

Rust: The safety of Haskell but with 1000x the performance. Probably my most used language these days.

C: Low level bit manipulation, portability, fast compile speed. Lingua franca of programming languages.

Python: Simple syntax, great at scripting prototypes and can provide a nice interface on top of native code if needed

These are the main ones I use these days.