At work we had some customers complaining of metadata not being removed on their servers.
nova --os-username username --os-password apigoeshere meta uuidgoeshere delete rax:reboot_window
It was pretty simple to do as a one liner right.
But imagine we have a list.txt full of 100 servers that need clearing for an individual customer, that would be a nightmare to do manually like above. so we can do it like:
for server in $(cat list.txt); do nova --os-username username --os-password apikeygoeshere meta $server delete rax:reboot_window; done
Now that is pretty cool. And saved me and my colleagues a lot of time.