I tried to simplify this, but man, I don't know if I can crush down these conditionals and enumerables.

gistfile1.rb

namespace :cleaner do
  task :find do

    models    = Dir.glob("app/models/**/*")
    methods   = %w[]

    models.each do |model|
      if File.file?(model)
        File.open(model).lines.each do |line|
          if method = method_name? line
            methods << method
          end
        end
      end
    end

    all_files = Dir.glob("app/**/*")

    methods.each do |method|
      use_count = 0

      all_files.each do |file|
        if File.file?(file)
        begin # Hack to handle binary files.
          file_count = File.readlines(file).grep(Regexp.new(method)).size
        rescue
        use_count += file_count unless file_count.nil?
        end

        puts "#{method} is a candidate for deletion" if use_count == 1
      end
    end
  end
end

protected
def method_name?(line)
  if line.match(/def ([a-z0-9._?!]*)/)
    line.match(/def (?:self.)?([a-z0-9._?!]*)/)[1]
  end
end