The core strengths of Erlang: Erlang has built-in support for concurrency, distribution and fault tolerance. There's many languages I enjoy, Erlang I've never learned (syntax and nobody to pay me to work with it) it fully to it's potential. I would also love to see a full blown SQL relational database in Rust and D, and maybe a NoSQL one as well.
See:
http://erlang.org/faq/introduction.html