Favicon for Frontend and Backend for Genesis powered websites --- place into "functions.php" of child theme or into a functionality plugin:

functions-childtheme.php

<?php
add_filter( 'genesis_favicon_url', 'ddw_custom_favicon_frontend' );
/**
 * (1) Favicon for Frontend
 *
 * @author David Decker
 * @link   http://twitter.com/deckerweb
 */
function ddw_custom_favicon_frontend() {

  return get_stylesheet_directory_uri() . '/images/favicon.ico';

}


add_action( 'admin_head', 'ddw_custom_favicon_backend_login' );
add_action( 'login_head', 'ddw_custom_favicon_backend_login' );
/**
 * (2) Favicon for WP-Admin & Login
 *
 * @author David Decker
 * @link   http://twitter.com/deckerweb
 */
function ddw_custom_favicon_backend_login() {

	echo '<link rel="Shortcut Icon" type="image/x-icon" href="' . get_stylesheet_directory_uri() . '/images/favicon_backend.ico" type="image/x-icon" />';

}