I'm using Avira. I'm not saying it's the best, but I'm satisfied with it. It's free, easy to use and not heavy on system resources. The free version does not have a firewall.
I used Trend Micro's PC-cillin (not free) in the past and also liked it. It's also fast and light. My only criticism was that it was rather slow in scanning compressed files like zip, cab, pk, etc.
The fact is that there is no single best AV. Each has its own strengths and weaknesses. I dislike Norton heartily because it tries to take control of everything.