Drupal: custom entity view modes.

foo.module

<?php

/**
 * Implements hook_entity_info_alter().
 */
function foo_entity_info_alter(&$entity_info) {
  $entity_info['node']['view modes']['another_teaser'] = array(
    'label' => t('Another teaser'),
    'custom settings' => TRUE,
  );
}

/**
 * Implements hook_preprocess_node().
 */
function foo_preprocess_node(&$vars) {
  if ($vars['view_mode'] == 'another_teaser') {
    $vars['theme_hook_suggestions'][] = 'node__' . $vars['type'] . '__another_teaser';
  }
}

node--article--another-teaser.tpl.php

<h1>Hello, Another teaser!</h1>