eek - EmsiSoft Emergency Kit

My first suggestion is Emsisoft Emergency Kit. I have been using this program for some years now and it became somewhat of a reference point to me. Without a definitive 'clean' from a-squared any further action is stopped. In its beginning it was a classic Anti-Spyware program, but it developed into a heavy-weight Malware scanner – completely free for private use. Viruses, Trojans, Backdoors, Worms, Dialers, Keyloggers and other vermin are safely detected and removed.

Though the context menu entry is now missing, the command line scanner makes up for that unfortunate decision. In various tests, a-squared gets almost 100% of the malware and if I were allowed only to use one program of this kind: a-squared it would be.