jQuery Solution
if you’re using jQuery you can use:
var $li = jQuery('ul > li:last-child','#nav1');
to select your last menu child.
Then after you select it you can chain it with another function:
$li.wrapInner('<input type="button" value="My Button!">');
Then all together:
jQuery(document).ready(function() {
// Cache your selection
var $li = jQuery('ul > li:last-child','#nav1');
// Replace it with your button
$li.wrapInner('<input type="button" value="My Button!">');
});
Pure CSS Solution
Setup your dropdown navigation:
PHP in the template:
<?php $args = array(
'sort_column' => 'menu_order, post_title',
'menu_class' => 'menu',
'include' => '',
'exclude' => '',
'echo' => true,
'show_home' => false,
'link_before' => '<span>', // Wrap your span here
'link_after' => '</span>' ); // close it with a span too
?>