WP-Cron Oneshot Job Scheduler for WordPress.
When activated, the WP-Cron Oneshot plugin will add a single "do nothing" task to wp-cron. This task will be scheduled to run immediately.
The task that gets added to wp-cron literally does nothing at all. It simply places something in the wp-cron queue so you can trigger a wp-cron run.
This can be useful for troubleshooting problems such as "Access Denied" errors in your Apache logs whenever wp-cron tries to run. If your XML-Sitemaps never seem to build automatically or your posts won't post at the scheduled time, it could be that the wp-cron job isn't running.
Once the task has finished, you can either leave the plugin activated or simply deactivate it.
If you ever need another task, just activate the plugin again.
For more information, see the WP-Cron Oneshot WordPress Plugin Homepage.