Use a custom walker:
class WPSE_33175_Simple_Walker extends Walker
{
public function walk( $elements, $max_depth )
{
$list = array ();
foreach ( $elements as $item )
$list[] = "<a href="https://wordpress.stackexchange.com/questions/33175/$item->url">$item->title</a>";
return join( "\n", $list );
}
}
… and then call wp_nav_menu()
like this:
wp_nav_menu(
array (
'theme_location' => 'your_registered_theme_location',
'walker' => new WPSE_33175_Simple_Walker,
'items_wrap' => '<nav>%3$s</nav>'
)
);