Free (no trial) antivirus
Avira AntiVir Free Edition
AVG Free Edition
Panda Cloud Anti-virus
Microsoft Security Essentials (MS seem to be saying don’t use it now?)
DrWeb CureIt! (On-Demand Scanner Only)
Clamwin (On-Demand Scanner Only)
Bit Defender Free Edition (very light, lack of settings)
Ad-Aware Free Antivirus+
Comodo Anti-virus + Firewall
PC Tools Free Anti-virus (discontinued)

I’d use AVG or Avira instead of Avast if I had to. Otherwise pay.

What experiences do you have of the above AV or other free ones?