function THEME_preprocess_node(&$variables, $hook)
    if (preg_match('//ARGUMENT$/', check_plain(current_path()))){
$variables['theme_hook_suggestions'][] = 'node__' . $variables['type'] . '__ARGUMENT';
    }

function THEME_preprocess_node(&$variables) {
  $variables['theme_hook_suggestions'][] = 'node__' . $variables['view_mode'];
}

function THEME_preprocess_node(&$variables) {
  $variables['theme_hook_suggestions'][] = 'node__' . $variables['type'] . '__' . $variables['view_mode'];
}

function HOOK_menu() {
   $items['node/%/argument'] = array(
    'page callback' => 'node_custom_view',
    'page arguments' => array(1, 2),
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}

function node_custom_view($arg1, $arg2) {
  $content = '';

  if (is_numeric($arg1) && $arg2 == 'argument') {
    $node = node_load($arg1, $vid = NULL, $reset = FALSE);
    $content = drupal_render(node_view($node, $view_mode = 'custom_view', $langcode = NULL));
  }

  return $content;
}