For me Nod32 hands down.
 
I have tried many virus killers, and used a few at work.
 
NOD32 has superb speed, very high detection rate, and importantly very low on system resources! Currently at work I use Sophos (slowphos as it's effectionately know in some circles). The resident programs etc take up over 15MB - similar resident protection in NOD32 use around 10MB.
 
 
 

McAfee is not that great & PC-Cillin is even worse. I highly recommend you going with Norton AntiVirus; It recieved the highest recommendations from PC Magazine.
 
Personally, I use Norton AntiVirus Corporation. There's no CD-Key's to hassle with, it uses less resources than the traditional Norton AntiVirus Pro (which means the computer runs more smoothly) & it uses pretty much the same virus scanning system = much better IMO.

pr man:
I can not speculate on Nod32 as I've not used it. I can strongly caution you to veer away from AVG. NAV & McAffee are good but they are the biggest resource hogs! I've opted for Trend Micro P-Cillin. Blazing fast speed and unparalleled updates. Some apps perform better for some machines vs. another which is a factor to consider as well.I hope that whatever your choice may be that it works for you, that's what really matters,
"Phine"
 

I have tried Norton which screwed my system up, also had manually uninstall it all. Antivir personal was pretty good but ugly and limited, Avg is intrusive and doesn`t allways update,Panda AV is garbage leaves stuff all over the place. Im using PCCillin at the moment which is very good built in web filter, built in firewall, realtime monitor, emergency lock easy updates and easy to use. God don`t i go on, anyway it`s usually down to personal preference and dosh.
NAV=0 AVG=7 ANTIVIR=8 PANDA=-10 PCCILLIN=10