Which is the best free antivirus?

I use avast, AVG, adaware, and windows defender. Because I use windows 8 I have the option to set which one I want as the "prevailing" antivirus (meaning windows 8 doesn't say "you should install more than one") and for that I chose avast, but I run them all at least once a month.

I am using Symantec..It's the best anti virus...

I use Avast Anti Virus also.

1.Avast
2.AVG
3.Ad-Aware Free Anti Virus
4. Avira
5. MSE

I am using net protector. It is best one but it is not free.

Microsoft security essentials along with good surfing habits.

I am using paid version of Webroot and it is perfect :)

Avast Free version and Trojan Killer paid works like a charm

Avast and AVG both are good.........
Not bad... :)

Microsoft security essentials is free for genuine windows users.

Quickheal anti virus

AVG... It's the best for me...

I use kaspersky and I think its good.

I am using Symantec..It's the best anti virus...