Clojure? It certainly has more syntax than many lisps, but still quite small. (And used in the mainstream world).

Smalltalk has been very influential in other ways, especially on Ruby. But yes, it would be great if more languages borrowed the "small simple core" bit (possibly adding some syntactic sugar, like ML does).

On the other hand, it's possible to make (core language + standard library) too small. A particularly bad thing to leave out is a module/separate compilation system, ensuring that a zoo of incompatible module systems will grow up.

You may enjoy Guy Steele's talk "Growing a Language": https://www.youtube.com/watch?v=_ahvzDzKdB0