All of Racket's `#lang` family of languages are implemented with macros on top of core Racket. For example, Scribble, mentioned in another comment, is the documentation language used to author the article, and the Racket docs[1]). Or Slideshow, Racket's programmatic Powerpoint alternative.

Try to add a static type system to Racket or Clojure. Oh but you don't have the ability to change the runtime system. With macros you can do it. See Typed Racket[2] or Typed Clojure[3].

[1]: http://docs.racket-lang.org/ [2]: https://github.com/plt/racket/tree/master/pkgs/typed-racket-... [3]: https://github.com/clojure/core.typed