Place this file somewhere and call it directly or via a cron tab. It allows you to flush all, or an array of pages. I'm using this to clear the cache of a pages that contain a date reference, at midnight. This is particularly useful when using "Disk Enhanced" page caching with the W3TC plugin, since WP_cron does not work with it. You might want …

W3 Total Cache Flushing

<?php
// Flush everything or just some pages
$flush_all_pages = false;

// An array of urls to flush (required if $flush_all_pages is false)
$urls = array(
	'http://www.example.com/',
);

//Set W3TC Constants
define('DONOTCACHEPAGE', true);
define('DONOTCACHEDB', true);
define('DONOTMINIFY', true);
define('DONOTCDN', true);
define('DONOTCACHCEOBJECT', true);

//Set WP Constants
define('DOING_AJAX', true); 
define('WP_USE_THEMES', false);


//Set headers
header('Content-type: application/json');
header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");

// Create a new empty output array
$output = array();

// Create a new empty array to output url outcomes
$urloutput = array();

// Add the list of urls to the output
if( $flush_all_pages ){
	$output['requested_urls'] = 'all';
} else {
	$output['requested_urls'] = $urls;
}

// Check if WordPress is available
if( file_exists($_SERVER['DOCUMENT_ROOT'].'/wp-load.php') ) {

	// If it is, require it
	require_once( $_SERVER['DOCUMENT_ROOT'].'/wp-load.php' );

	// Tell us that WordPress is avaiable
	$output['wordpress_exists'] = true;

	// Check if W3 Total Cache's page cache flush (by url) is available
	if( function_exists('w3tc_pgcache_flush_url') && function_exists('w3tc_pgcache_flush') ) {

		// Tell us that the w3tc function exists
		$output['w3tc_exists'] = true;

		//Flush the entire cache cache or the provided pages
		if( $flush_all_pages ) {
			$result = w3tc_pgcache_flush();
			$output['w3tc_feedback'] = $result;
		} else {
			foreach ($urls as $url) {
				$result = w3tc_pgcache_flush_url($url);
				$urloutput[$url] = $result;
			}
			$output['w3tc_feedback'] = $urloutput;
		}

	} else {

		// WordPress exists but we have no w3tc stuff
		$output['w3tc_exists'] = false;
		$output['w3tc_feedback'] = false;

	}

} else {

	// No WordPress, no nothing
	$output['wordpress_exists'] = false;
	$output['w3tc_exists'] = false;
	$output['w3tc_feedback'] = false;

}
// Add a timestamp
$output['timestamp'] = date('c');

$json = json_encode($output);
// Send the array json_encoded back to the browser (optional)
echo $json;

// Finally send an e-mail to mail the results (optional)
$mail_body = $json;
$headers[] = 'Content-type: text/html';
wp_mail('mail@example.com', 'Example.com Cache Flush', $mail_body, $headers);

Very useful.
Used it to create a script that automatically flushes (and then visits) a lists of products, so they're always warm.