Essential penetration testing tools

I found a good blogpost that lists the most essential tools for penetration testing:
http://www.paladinsec.com/penetration-testing-tools-equipment/
To summarise the post, the following tools are a good start:
– Laptop
– Vulnerability scanner (OpenVAS, Nexpose, Nessus)
– Word processor (Word, Writer)
– Internet access
– Liability insurance
– Virtualization (VirtualBox, VMware, Hyper-V)
– Kali Linux and a virtual Windows PC
– Network cables and a switch