Writing a method that is accessible from any views as well as any controller

HI guys where should i have to write the method that it is
accessibible from any controller and any views. When i write the
method in application controller then it is accessible in controller
only and when i write it on application helper it is accessible on
views only. I even tried to write it as module in the lib and included
in the application controller, in that case it becomes inaccessible in