Mine is Avira and Kaspersky i love both of them but currently am using Avira Internet Security Suite.
kappersky. there's a website where a guy did an independent study to figure out which antivirus was the best. i can't find it...
I +1 avast because it catches everything I come across whether it's malware or spyware and it doesnt seem to slow your system down like AVG started to about a year ago. Avast is free and simply uses less system resources than anything out there to do it's job. Another poster mentioned using Zonealarm .. I really liked that to monitor incoming/outgoing connections. Both in combination is very powerful.
I use eset smart security for years and it works really good, never had any problems with either viruses or trojans or anything... and license renewal is not that expensive...
I remember Kaspersky leaving traces of itself when being uninstalled and causing all sorts of problems. Is this still an issue? Also norton or Mcafee had this problem and whichever one it was even had to go as far as making a special uninstall tool for itself so it was properly uninstalled. I've had a bad taste for all of these ever since. =/