While I'm thinking about it, I came up with a seemingly good use case for wasm over the weekend, but don't expect I can carry the project to completion, if somebody else wanted to.
This blog post laid out simple rules for validating the complexity of passwords, and one if it's biggest points is that people should deny users the ability to use known common passwords. Basically, these days it is best practice to use the many leaked password lists as a blacklist, since users employing these passwords are trivially targeted.
So the idea here is to take the fst crate and encode that giant password list into a hopefully small FST, and do the search fast and compactly. Create a C interface so anybody can use it server-side, then bind that C interface to a JS interface via wasm so anybody can use it client-side. Package it up to produce builds for common platforms and do a 'Show HN' to get some karma.
I did a prototype over the weekend but seems likely won't get much farther any time soon: https://github.com/brson/pwrabs