possibly the funniest controller before filters we have in our codebase

accounts_controller.rb

class AccountsController < ActionController::Base
  before_filter :lock_out_annoying_scammers
  def lock_out_annoying_scammers
    if signed_in_user && signed_in_user.email =~ secret_hacker_regexp
      logger.warn 'One of those annoying scammers has tried to access the accounts controller'
      redirect_to 'http://www.amazon.com/Hackers-Jonny-Lee-Miller/dp/6305047456/' and return
    end
  end
end