I've used Bitdefender (2009, 2010, 2011, 2012), Kaspersky, McAfee, ESET Nod32, AVG, ThreatFire, Avast, Avira, and Windows Defender (Windows 10). Among these, I have retained Avira.
I used to have a paid version of Bitdefender (that's why I've been using it for over three years back then), but...