Based on reports it is "Kaspersky". Followed by "Nod32" and "Symantec" in a very close second/third - in no particular order.
Avast and AVG have some of the poorest detection ratings of the "top" virus engines. But they are free
.. Avast! is better than AVG IMO. The community is great too.
As for firwall? For a s/w firewall, I'd just stick with Zone Alarm pro. For a free version, Zone Alarm (vanilla) is great.