[bikeshack]

I like tools that rather than scan for signatures (which can be polymorphic in nature and bypass AV), they can look for out-of-place behaviour on the OS. The Sysinternals Suite is great for malware hunting: https://technet.microsoft.com/en-us/sysinternals/bb842062

And things like Reason Core are brilliant for nuking any rootkits that somehow get on to a system https://www.reasoncoresecurity.com/

Malware has grown up and is now residing in hardware and can survive entire OS re-installs. I feel sorry for Windows users these days because malware has grown up and it is not as obvious you have malware. In the past there were obvious signs you were infected and the malware made itself known (sort of stupid when you're an attacker really).

Also some of the 'second opinion' tools are interesting too:

http://www.surfright.nl/en/hitmanpro