Applying the experimental Ruby 2.0 Refinements feature to the classic FizzBuzz challenge. (http://www.codinghorror.com/blog/2007/02/why-cant-programmers-program.html)

fizz_buzz_refinement.rb

module FizzBuzz
  refine Fixnum do
    def to_s
      if self % 3 == 0 && self % 5 == 0
        "FizzBuzz"
      elsif self % 3 == 0
        "Fizz"
      elsif self % 5 == 0
        "Buzz"
      else
        super
      end
    end
  end
end

(1..20).collect{ |n| n.to_s }.join(', ')
# => "1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20"

using FizzBuzz

(1..20).collect{ |n| n.to_s }.join(', ')
# => "1, 2, Fizz, 4, Buzz, Fizz, 7, 8, Fizz, Buzz, 11, Fizz, 13, 14, FizzBuzz, 16, 17, Fizz, 19, Buzz"