Buenas,
Esto te deberia funcionar:
Código PHP:
<ul>
<?php
$usernames = $wpdb->get_results("SELECT user_nicename, user_url FROM $wpdb->users ORDER BY ID DESC LIMIT 1");
foreach ($usernames as $username) {
echo '<li><a href="'.$username->user_url.'">'.$username->user_nicename."</a></li>";
}
?>
</ul>
Un saludo!