I'll start. I really like coffeescript for a number of reasons. -It protects you from a lot of javascript's gotchas like globally scoped variables. -I've come to realize syntactically significant whitespace languages are cleaner once you get used to them. -I write about 30% fewer lines than javascript.
Elm. It is very different to JavaScript, as it is a functional reactive language, but it compiles down to JS, can interact with it and is quite powerful. Check out some examples to see the syntax. As objects are immutable, you describe everything as-it-is, instead of how-it-changes. That means, once you get the functional way of programming, you will have way less headaches with coding and debugging.