Non-interactive shell scripting. It's actually the best language in this niche, outclassing Perl and Tcl in terms of features and Python/JS in terms of expressivity.

General purpose scripting. Orders of magnitude fewer packages and batteries than in Python or Ruby, but it does have a package manager and a bunch of libs for typical tasks. It's also capable of calling Python code almost seamlessly. For small (1 file) scripts, the expressivity of Raku means often half the lines of equivalent Python code, unless you hit a package that Python has and Raku doesn't.

Everything related to text processing. The grammars parsed by Grammars don't have to be context-free. Parsing just about anything is a joy. Also, light data mangling - if it fits in RAM, you might not need any other tool (like R/Pandas).

It's also a general-purpose, gradually typed, JIT-compiled, multiparadigm (OO, FP, procedural, array) language, so you can use just about anywhere you want. It's less great for mission-critical things (error handling is peculiar) and shell one-liners (the JIT takes a toll on startup time). It has a REPL, instead.