It's often been the case that a difficult problem can be made easier by transforming it into a different representation.  Nowhere is that more true than in mathematics and the pseudo-mathematical realm of programming languages.

For example, LISP, Python, and Ruby all offer beautiful and concise constructs for operating on lists of things.  In each of them, you can make a function which iterates across a list, performing some operation on each element, and returning the resulting list.  C, C++, and Java do not offer any similar construct.  In each of these languages, iterating a list is a control-flow structure that requires multiple lines to express.  More significantly, the function expression of list comprehension can be composed. That is, you can embed a list comprehension structure inside of another function call or list operation.  In reading Programming Collective Intelligence, which uses Python as its implementation language, I've been amazed at how eloquent complex operations can be, especially when I mentally transliterate the same code into Java.

In the evening keynote at QCon, Richard Gabriel covered 50 language topics, with a 50 word statement about each---along with a blend of music, art, and poetry. (If you've never seen Richard perform at a conference, it's quite an experience.)  His presentation "50 in 50" also covered 50 years of programming and introduced languages as diverse as COBOL, SNOBOL, Piet, LISP, Perl, C, Algol, APL, IPL, Befunge, and HQ9+.

HQ9+ particularly caught my attention.  It takes the question of "simplifying the representation of problems" to the utmost extreme.

HQ9+ has a simple grammar.  There are 4 operations, each represented by a single character.

'+' increments the register.

'H' prints every languages natal example, "Hello, world!" 

'Q' makes every program into a quine.  It causes the interpreter to print the program text.  Quines are notoriously difficult assignments for second-year CS students.

'9' causes the interpreter to print the lyrics to the song "99 Bottles of Beer on the Wall."  This qualifies HQ9+ as a  real programming language, suitable for inclusion in the ultimate list of languages.

These three operators solve for some very commonly expressed problems.  In a certain sense, they are the ultimate solution to those problem.  They cannot be reduced any further... you can't get shorter than one character.

Of course, in an audience of programmers, HQ9+ always gets a laugh.  In fact, it was created specifically to make programmers laugh.  And, in fact, it's a kind of meta-level humor. It's not the programs that are funny, but the design of the language itself... an inside joke from one programmer to the rest of us.