I am always looking for cool Knowledge Base Articles from VMware that I think are helpful for the admins. One question that I have seen come up in the past is creating custom firewalls rules on vSphere hosts. I found an article today discussing how to Create Custom Firewal Rules in ESXi 5.0 via the command line. Its a nice VMware KB Article, very cool.
For full details on creating custom firewal rules in vSphere 5.0 via the command line check out the KB Article.