Crystal, but only because I’m a full time Ruby on Rails (and sometimes Hanami!) programmer.
It’s fantastic, and I had an excuse to use it at work when we needed to gather PHP Watchdog logs from a MySQL database and format, output them to STDOUT in a Kubernetes environment. (This was necessary for our log monitoring tools expecting data in a standard way, AKA not connecting to a database. 🤦♂️)
I know there are perhaps better options out there (Go, Rust, etc.) but from a Rubyist’s point of view Crystal gives you that “flow” from working in a beautiful language but with the performance boost of compiled software.