NeWT Scanner

[Stalemate]

http://www.tenablesecurity.com/newt.html

NeWT is a Windows equivalent to Nessus (http://www.nessus.org/).

If you ever need to scan for vulnerabilities, this is an excellent tool to do so.

[Poseidon]

Great utility, but a little pricy

[Coyotemac]

Great utility, but a little pricy

Haven't checked the price on it but I heard that compared to some of the other products out there (ISS, Retina, Foundscan, etc) it wasn't that expensive - I think an "insultant" license for ISS is extremely expensive (I don't know for sure but I heard between 50 -100K).

I've used Nessus, NAI Cybercop (I think it is dead now), ISS, foundscan, to audit all types of systems and I'm most impressed with Nessus.

Newt uses the same nasl scripts as nessus and they are usually very quick to release new ones as vulnerabilties are reported - plus you can view the code to independently confirm the results.