Kaspersky as first choice - paid. It's strong all-round in suite form, but the AV is second to none. click here
Note that Steganos AV uses exactly the same engine and is a little cheaper. (I haven't used it in suite form, but believe it has fewer features). click here
AOL Antivirusshield also uses the Kaspersky AV engine, so SHOULD be excellent. click here?
I have used AVG antivirus - free alternative, and that works just fine in most situations. It isn't quite as customisable, or as informative, as Kaspersky. I prefer it to AVAST (also free), but haven't used the latter for a couple of years.
Overall, I think it is just worth having the paid - for forms (especially as a bit of hunting gives some excellent prices)
There's a free 6 month offer for Panda Internet Security on Computer Shopper (hiss, boo) this month (well, it is August isn't it??). I didn't like Panda 2006 much, and you do ask for AV not suite. Worth considering, and you can just throw the "useless" magazine in the bin :-)