code.php

$titles = array();

foreach ($order->products as $product) {
  $titles[] = $product->title;
}

// dpm($titles);

$titles = implode('<br />', $titles);

print $titles;

custom_ubercart_events.info

name = custom ubercart events
description = "My description"
package = Custom

version = 7.x-1.1
core = 7.x

custom_ubercart_events.module

<?php
/**
 * @file
 * Code for the custom ubercart events module.
 */

/**
 * Implements hook_uc_checkout_complete
 */
custom_ubercart_events_uc_checkout_complete($order, $account) {
  kpr($order)
}