HitmanPro is an anti-virus program that describes itself as a second opinion scanner that should be used in conjunction with another anti-virus program that you may already have installed.  If malware slips past your anti-virus software, HitmanPro will then step in to detect it.  Though SurfRite bills themselves as a second opinion scanner that does not mean that you cannot use the program as your primary anti-virus product. This is because its scanning technology not only incorporates its own virus definitions but also has the ability to scan files on your computer with the definitions of 5 other anti-virus vendors.

Emsisoft Emergency Kit is a collection of standalone security programs and scanners that can be run from a USB key, bootable CD/DVD, or from within Windows Safe Mode without having to download and install a full security product.  This program is very useful for infections, such as Ransomware,  that cannot be removed while the infections are active or while logged into Windows.  

ComboFix is a program, created by sUBs, that scans your computer for known malware, and when found, attempts to clean these infections automatically. In addition to being able to remove a large amount of the most common and current malware, ComboFix also displays a report that can be used by trained helpers to remove malware that is not automatically removed by the program.

The Sophos Virus Removal Tool is a stand-alone program that allows you to perform a quick scan of your computer for computer viruses.  If any infections are found it will attempt to remove them for free. As this program only scans your computer and remove any infections it finds, it can be used even if you have another anti-virus product installed.