For example, high performance servers (voltlane.net), programming languages (https://github.com/HF-Foundation, https://github.com/lionkor/mcl-rs, and one private one), webservers (beampaint.com) and lots of other domains.
Rust is close to C++ in that it is a systems language that allows a reasonable level of zero-cost abstractions.
Writing the compiler toolchains that Rust depends on, industry standards like CUDA, SYSCL, Metal, Unreal or the VFX Reference Platform.
Maybe cranelift will eventually surpass LLVM, but there isn't currently much reason to push for that.