Here's a few I've used and found quite effective.
|Kaspersky Virus Removal Tool 2011|
|Microsoft malicious software removal tool|
There's always malicious software out there designed to evade detection from popular antivirus software. With these three, you've got your bases well covered in most cases. It's rare to find viruses evading these three in combination.
Technician's toolbox - malicious software removal tools
Technician's toolbox - system maintenance tools
Technician's toolbox - Ultimate Boot CD