Windows only: Security applications frequently make themselves quite a bear to truly remove. That's great when their stubbornness protects you from malicious software—not so great when you just want them gone.
AppRemover is a free application that specialises in stubborn, clingy security applications. Why would you want to remove security software? If you're replacing one security application with another or have a conflict between two security applications you have installed, it can be tricky to fully remove the offending application completely. AppRemover is a simple application with a basic wizard-driven menu system. It scans your system for security applications against an extensive list—you can view it here—and then you can remove all or selected security applications from your computer. AppRemover is freeware, Windows only. Looking for a more general-purpose remover? Hit up the previously mentioned (and much-loved) Revo Uninstaller.