Malwarebytes, it just seems to work better than anything else I've found. It's been so useful that we purchased the Corporate version for our SMB network. I use it and CCleaner on every machine I work on.

Spiceworks Network management and monitoring. Free application, really good corporate support for this product and the best help forums of any site I've ever used. Over a million members from around the world and the most helpful people around and many very knowledgeable ones willing to help.