A friend of mine, Professor Dave Mason from Toronto Metropolitan University and the Chair of the Computer Science Department, loves Rust and Smalltalk. These are the only two programming languages he uses these days. (He's used dozens of languages.)

Professor Mason loves Rust for its safety and reliability, and he loves Smalltalk for its rapid development and productivity. These are the best-in-class languages for their respective domains.

FYI, last year, Smalltalk celebrated 50 years with a huge birthday bash: https://medium.com/p/bed82541b7db.