I’ve mentioned that I’m using Comodo Firewall as my software firewall solution. Version 3 was even better than version 2, with low CPU utilisation (even while engaging in heavy P2P sessions) and secure (ranked consistently near the top in the Matousec firewall tests).
And now version 3.5 (renamed the Comodo Internet Security) has been released and featuring an optional anti-virus component. I cannot speak for the efficacy of the anti-virus component, but the engine feels very light, and the definitions get three or four updates a day. If the quality of the firewall is anything to go by, the anti-virus engine is one to keep an eye on.
Best of all? Its free (as in beer).
The final build is available in the forums, but the public facing sites have not been updated yet.