If you mean Best Free Antivirus.. I would vote for AVIRA. I am using this since 3 years and no complaints. I am most of the time online and never faced any big threat of Viruses. AVIRA is safe guarding me very well. I visit almost all genres of sites.
According to me Kaspersky .......... I also use it in my computer and i am fully protected from virus
I use malwarebytes or however its actually spelled (it's so late and im so drunk...so glad the giants won) and I love it cause it's like an additional lil firewall blocking me from accessing IPs its database blacklists. Add that with peerblock, windows firewall, and a few other hoops to jump through, and I'm surprised I can even access the internet at all. also, don't ever believe someone is drunk if they type poorly. only girls (sexy girls) do that. so do them. haaaaaa
I do vote for Avast for personal/home use. It is very powerful antivirus with many great security tools like web shield, mail shield etc. All we get for free (yes, we get 1 year licensee and we can renew it after 1 year for free)..