Nim programming language
Nim is the language I have always thought was a brilliant idea that I never get to use.  It's a shame.<p>Nim is to C/C++ as CoffeeScript is to JavaScript.  A highly extensible template language atop a portable language with libraries for practically everything.<p>So why haven't I hopped on the bandwagon?  Outside of C++, C, and Fortran - the only way I have ever learned a new language is through using a REPL.  How much of Python's and MATLAB's (and maybe even Julia's) success is due to having a brilliant REPL?<p>I am not complaining, and I do not have any free time to fix it.  But man... if Nim just had a killer REPL that allowed me to slowly learn the language properly while not being blocked from my daily work... it would be just killer!