Tested Language : Befunge-93

    Befunge (or more precisely Befunge-93) is a stack-based
    esoteric language in which programming constructs are laid
    out on a two-dimensional "playing field."  Befunge was
    invented by Chris Pressey in 1993, as a language that would
    be as hard to compile as possible.  Several extensions to
    the Befunge-93 language have been made, including Funge-98,
    a multithreaded N-dimensional language incorporating
    time-travel primitives.  Since the closing of Pressey's
    Cat's Eye Technologies website, the Befunge programmer has
    gone from endangered to nearly extinct.

    http://sourceforge.net/projects/funge/

    (parts lifted from Wikipedia:Befunge)