What is the best free AntiVirus software?

[coach]

I'm going with AVG. Any other recommendations or experiences to support or contradict my selection?

[Millwright]

I have always heard good reports on AVG, but I have always used Avast.
Just got used to it I guess.

[bobletman]

Go with avast its the best antivirus you can get but AVG is good to.

[Zenphic]

Avira Antivir is also another good antivirus

[madspartus]

avast for years

[IDKFA]

I've been using AVG for a few years, and while they're reliable (it's a loss-leader for their big powerful enterprise antivirus program) the marketing has been getting a bit pushier lately - not as bad as ZoneAlarm pushing paid versions, but still not as pleasant as it once was - they maintain daily updates with the latest badware updates.

Word of warning, I've heard things about it not playing well with (if I recall) Source engine games, so it may prove necessary to kill AVG before a bout of Team Fortress.

[khelben1979]

I experience Sophos to be the best!