Powershell. The only tool that knows how to talk to all the different frameworks in Windows is Powershell. No other tool can talk to .NET, COM, WMI, native APIs (via P/Invoke), and external stdio based tools. If you can't do the automation you want using something in one of the above frameworks, you've got bigger problems than finding a good automation tool.

Since the test guy usually has to be a part time sysadmin too, you should be aware of these tools:

System update readiness tool: http://support.microsoft.com/kb/947821/en-us
WMI diagnostic utility: http://www.microsoft.com/downloads/en/details.aspx?familyid=d7ba3cd6-18d1-4d05-b11e-4c64192ae97d&displaylang=en
gplogview: http://www.microsoft.com/downloads/en/confirmation.aspx?familyId=BCFB1955-CA1D-4F00-9CFF-6F541BAD4563
Windows SDK (including debugging tools for windows): http://www.microsoft.com/downloads/en/details.aspx?FamilyID=35AEDA01-421D-4BA5-B44B-543DC8C33A20
ollydbg: http://www.ollydbg.de/
sysinternals suite: http://technet.microsoft.com/en-us/sysinternals/bb842062
Windows Management Framework: http://support.microsoft.com/kb/968929
WDK: http://www.microsoft.com/downloads/en/details.aspx?displaylang=en&FamilyID=36a2630f-5d56-43b5-b996-7633f2ec14ff
WAIK: http://www.microsoft.com/downloads/en/details.aspx?familyid=696DD665-9F76-4177-A811-39C26D3B3B34&displaylang=en
Windows 7 SP1 WAIK supplement: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=0AEE2B4B-494B-4ADC-B174-33BC62F02C5D

If XP is involved, check out Windows SteadyState. It's like deepfreeze, if you've ever used that. qemu is also a great way to boot test machines and capture output at scale; using CoW disks you can have fresh machines every time you boot regardless if the test machines are XP or not.

Lockheed Martin recently put out a press release about their magnetic communications system (MCS), which works at distances of up to half a mile through solid rock:

http://www.popsci.com/technology/article/2010-08/lockheed-develops-magnetic-communication-mine-safety

Although the MCS probably uses large coils and low wavelengths on both sides to achieve that impressive distance, typical RFID cards have small coils. To make up for this, very strong digitally controlled magnetic fields could be used to couple to a coil from far away. For example, see this implementation of a static 0.7 tesla magnet:

http://www.technologyreview.com/biomedicine/25527/page1/

A strong enough, highly directional magnetic field and a sensitive enough detector could couple all the way to the theoretical maximum distance permitted by the RFID card's frequency. Like the MCS, that distance is one third the wavelength of 125 KHz (1.5 miles), or half a mile.