add MCE buttons to WordPress

function enable_more_buttons($buttons) {
  $buttons[] = 'hr';
  $buttons[] = 'anchor';

  /*
  Repeat with any other buttons you want to add, e.g.
      $buttons[] = 'fontselect';
      $buttons[] = 'sup';
  */

  return $buttons;
}
add_filter("mce_buttons", "enable_more_buttons");