`jq` is pretty much the only one solving a real problem that no existing tool solves IMHO. Most of the others are rewrites for some opinionated 'better' (faster, syntax highlighting, written in Rust or whatever...).
As stated elsewhere linqpad is really great for testing ad-hoc, throwaway C# code (much more than just linq expressions). It kind of like a REPL for .net.
If you're doing any Entity Framework development, you should be using LinqPad and checking generated SQL for pretty much every canned (read re-used, not inline) query you write. Somethings can be unexpectedly ugly and badly performing if not optimized properly.
