Agax
Complex but powerful anti-virus tool

Disinfectant
No longer current (so don't rely on this alone) but still excellent for older viral attacks.

Tracker
A generic 'suspicious activity' blocker

vScan 1.6.1
General-purpose anti-virus tool, includes a Control Strip module for quick access

WormScanner
Tracks down and kills many variants of the destructive 'auto-start' worm virus