None. If you know what your doing, you don’t need anti-virus software. If you don’t know what your doing, anti-virus software isn’t going to save you. The fact of the matter is, the built in firewall in your OS is probably enough as long as you don’t download random files.
I live and die by Avast. I like to think I know what I’m doing, but you can never be too safe with all the exploits floating around.
avg antivirus
zonealarm firewall
also run ad-aware and spybot every once in a while
ESET Smart Security 4.0 for me! And I love it! In fact I started using ESET since last year and no problems since then!
McAfee Total Protection for Small Business @ the office
AVG Free on my Netbook
I run my home office desktop without any Anti Virus.
I usually run Kaspersky on my personal computers and any computer I maintain for friends and family. Kaspersky has been fantastic. I would recommend Kaspersky to anyone who wants good reliable protection. IMO, McAfee is something I use at work, because I have no choice, and would not recommend to anyone.
I am using free AVG antivirus and Avast. It works well
Im using NOD32, been using it since 2004 and its great. Has a very low memory print and is very fast when scanning.
Sure. You are aware that you can get trojan horses / virus through a lot of means? Just viewing a internet page can get you infected without a proper AV.
This
NOD32. Been pretty good so far but have had troubles with ICS with my 2nd comp.
Heh, tell that to my relative who has an interesting story. After a fresh reformat, they installed the ethernet driver…and had to reformat again because the second they were open to the internet, a worm came through. no joke. Too bad the windows firewall didn’t catch it -_-;
AVG at home and sophos at work
Trend Micro OfficeScan
AVG Free works great however.
AVG Anti-Virus. Even recommended it to a young lady at the local Walmart who was trying to buy Norton Anti-Virus from Symantec. Once I told her AVG was far better (not to mention free) she put it (Norton) back.
None and I am not being big headed saying that. My circumstances and experiences have led me to not require one. I’ve been using PCs for about 12 years now and I’ve never needed AV, they’re just an annoying waste of resources imho. I’ve played around with a few but removed them and I haven’t downloaded an av program for years now. I bought or rather my mother bought me Norton in 2004 and it lasted about 10 minutes on my system, its a total resource hog of a program. I packed it up and had my mother send it back to QVC.
The worst virus I have had in terms of it affecting my use of the computer is win32.parite and that was years ago. If I download something off the net that I am not sure of I scan it with bit-defender’s online virus scan which is free. Sometimes it would pick something up in a file I downloaded and then I would just scan my entire system just to be sure it hadn’t spread.
Over the last few years I have become more aware of what I am downloading and bit-defender doesn’t pick anything up if I scan the file. I sometimes double check with another free online virus scanner, but when push comes to shove I trust bit-defender. Once in a blue moon I will scan my entire system with it along with spybot and adaware, but they rarely find anything; bit-defender never finds a virus any more.
If you keep clear of dodgy stuff, keep a relatively low web profile, don’t enter your email into any old web form, and be shrewd you shouldn’t need one. Know your system, its quirks and idiosyncrasies and you should be able to detect when something is up with it as its behaviour will change. The firewall I use is Sygate Personal Firewall which is old and crap compared to the modern ones, but that’s all I use it for is to allow or disallow apps to communicate to and from the net. I tried comodo which is a great firewall, but it annoyed the hell out of me and was promptly removed. My real firewall is on my router and it does a good job at protecting me.
To some extent I echo what ben said, but I think you should have another firewall besides the windows one. I like to know what apps are trying to communicate with the web.
I like NOD32
ESET NOD32 – at work
Symantec – at home
Norton blows… no offense
Tons of advertisement… resource intensive… = Norton
You are basically paying for there adverts
AVG Free Kicks Butt 
I used to use mcafee before moving to Mac. Now I don’t need to use any anti-virus software.
AVG anti-virus 
Im using ESET Smart Security
Is Mac better then Windows 7?