Aside from the actually good use cases other comments have mentioned, one idea I've played around with is using it for augmenting an Elixir app with code that can be run in both the browser and the server - use a NIF to run the Rust code server-side, compile it to WASM to run in the browser. The idea that inspired me was writing input validation code, running it both in the browser for greater responsiveness and on the server for making sure inputs get validated, using the same source code so those don't get out of sync. It's probably not worth the added complexity, but it's kind of neat.