This is untested for obvious reasons. For the same reasons, i've uploaded it as a txt file instead of as a ps1.
This powershell function should sequentially remove from your VIServer all: snapshots, templates, VMs, resource pools, folders, clusters, datacenters virtual port groups, virtual switches, network adapters, host network adapters, storage adapters, stop all vm host services, remove all hosts, and host accounts.
It's usefulness is limited to those having a test VIServer that needs to be stripped and started from scratch. I don't recommend you execute this function, it's too dangerous, but the evil had to be released...
USE AT YOUR OWN RISK!