If you don't want to use a contrib module (one does exist), you can implement [`hook_entity_info_alter()`][1] to add the view mode yourself. For example this code adds a new view mode called "Test View" to the node entity type:

    function MYMODULE_entity_info_alter(&$info) {
      $info['node']['view modes']['test_view'] = array(
        'label' => 'Test View',
        'custom settings' => TRUE
      );
    }

After a cache clear that view mode will appear in all the places you'd expect (manage display, views, etc.)

[1]: http://api.drupal.org/api/drupal/modules%21system%21system.api.php/function/hook_entity_info_alter/7