Functional programming wise I like Erlang. It’s simple, to the point, surprisingly powerful with a few charming quirks. Elixir is fine but I like Erlang better. I am interested in the new set-theory type system for Elixir though. The initial presentation looks really good.
I haven’t really given Haskell a chance, but when I dabbled with Elm I liked the approach. Elm is more simple of course. What I don’t like so much about Haskell is that there are several compiler extensions and even if you decide for yourself not to use them to keep it simple they might sneak into your projects via packages. And then you still have to learn the underlying concepts.
Compared to Haskell I prefer Ocaml, although that has also some charming quirks. In total it feels to me that in functional programming the language communities there are a lot of discussions about concepts and less about actual coding. I was a fan, but I gravitate back to procedural. Especially as a lot of procedural languages have some functionality now that used to be associated with functional programming.
Scala looks great, but I haven’t got around it.
A few interesting variances of Ada are Austral, which provides a linear type model that gives interesting guarantees for memory but also file management (and more). A really interesting approach. Austral is also quite new and still growing.
Then there is HAC which currently covers a subset of Ada and has a compact compilation suitable to embed into other programs.
Last but not least Nim. A very pleasant language. Versatile, fast and you can choose to use it with or without garbage collector. This is in my view a great option as there are many problems that benefit from a garbage collector but sometimes you need to know where your bits and bytes are exactly.