Here's all I came up with:

class Hello; def self.world!; [self, __callee__].join(' '); end; end

puts Hello.world!

Only works with Ruby 1.9 though...

On Feb 29, 7:06=A0pm, Matthew D Moss <matthew.m... / gmail.com> wrote:
> The three rules of Ruby Quiz 2:
> 1. =A0Please do not post any solutions or spoiler discussion for this =A0
> quiz until 48 hours have passed from the time on this message.
>
> 2. =A0Support Ruby Quiz 2 by submitting ideas as often as you can! (A =A0
> permanent, new website is in the works for Ruby Quiz 2. Until then, =A0
> please visit the temporary website at
>
> =A0 =A0 =A0<http://matthew.moss.googlepages.com/home>.
>
> 3. =A0Enjoy!
>
> Suggestion: =A0A [QUIZ] in the subject of emails about the problem =A0
> helps everyone on Ruby Talk follow the discussion. =A0Please reply to =A0
> the original quiz message, if you can.
>
> -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=
=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-
>
> Hello, world?
>
> The first program any new programmer typically sees is one that =A0
> prints out "Hello, world!" to the console. This tends to be something =A0
> experienced programmers also see when learning a new language. The =A0
> first Hello World program was written in B [1] by Kernighan and =A0
> looked like this:
>
> =A0 =A0 =A0 =A0 =A0main( ) {
> =A0 =A0 =A0 =A0 =A0 =A0 =A0extrn a, b, c;
> =A0 =A0 =A0 =A0 =A0 =A0 =A0putchar(a); putchar(b); putchar(c); putchar('!*=
n');
> =A0 =A0 =A0 =A0 =A0}
>
> =A0 =A0 =A0 =A0 =A0a 'hell';
> =A0 =A0 =A0 =A0 =A0b 'o, w';
> =A0 =A0 =A0 =A0 =A0c 'orld';
>
> Most programmers are probably more familiar with the typical C =A0
> implementation:
>
> =A0 =A0 =A0 =A0 =A0main() {
> =A0 =A0 =A0 =A0 =A0 =A0 =A0printf("Hello, world!\n");
> =A0 =A0 =A0 =A0 =A0}
>
> Ruby can present the same output very simply:
>
> =A0 =A0 =A0 =A0 =A0puts "Hello, world!"
>
> But that's too simple... I mean, really... *anyone* can print a =A0
> simple string to standard output. Can't we get more interesting? =A0
> Hmmm, how about:
>
> =A0 =A0 =A0 =A0 =A0puts sprintf("%s, %s!", "Hello", "world")
>
> Eh, that looks too much like C. Maybe...
>
> =A0 =A0 =A0 =A0 =A0puts %w(Hello world).join(", ") + "!"
>
> Yeah, that's definitely looking Ruby-ish.
>
> Your task this week is to print "Hello, world!" to standard output =A0
> using Ruby in atypical fashion. Some guildlines:
>
> - DO submit multiple variants in your submission, but we don't need =A0
> 100 variants from everyone. Try to limit yourself to your best dozen.
> - DO keep things reasonably simple. I would expect many solutions to =A0
> be one- or two-liners, some solutions to involve classes and =A0
> functions, and a variety in-between. But we're looking for Ruby-isms, =A0
> not volume of code, so don't write pages upon pages of code just to =A0
> print "Hello, world!"
> - DON'T obfuscate unnecessarily. We're looking for interesting Ruby =A0
> tricks, not utter confusion. A little obfuscation is okay, but a lot =A0
> is to be avoided.
> - DON'T send me my own examples from above. I already did them. Do =A0
> other stuff. It *is* okay if your solution is similar to mine, =A0
> provided you make some interesting modifications.
>
> [1]http://cm.bell-labs.com/cm/cs/who/dmr/btut.html