Windows Defender's good, except if the malware has the same name as the targeted DLL (HitmanPro's been seeing more of those over the past year) or is a bootdisk virus. For grandma, however, it's perfect.
ESET's pretty solid.
Avira's built with German engineering but is equally heavy on processing power. Also, the installation and license activation process isn't very intuitive. If you're running a network, this might be an effective choice.
Norton is being phased out of existence, as Google downgraded Symantec to subCA status last year for selling corrupted SSL certs.
Avast and AVG are notorious for false positives, even more so for doing it to each other on a regular basis.
McAfee is okay, but it's pre-installed on Windows 10 as an opt-in antivirus. It doesn't really matter if you opt-out, though, the next update forces the activation.
Zemana's awesome, but you have to remember to use its built-in uninstaller or else you'll end up with orphaned kernel files that are a headache to remove.
Kaspersky's safe, and also reliable.
I ended up going with Dr.Web about a month ago. So far everything's been running smoothly, I haven't been hit from all sides by malware, and the system maintenance is much easier.
CCleaner is a maintenance program; it's not really an antivirus, but it's still effective at optimizing your computer.
RogueKiller, MalwareBytes, HitmanPro and HitmanPro.Alert are second-opinion scanners, which means that they catch whatever Windows Defender, BitDefender, ESET, Kaspersky, AVG, etc. miss. It never hurts to have a backup.
All major AV software these days utilizes some form of cloud-based upload scanning, in case they detect an unfamiliar file that may (or may not) be a virus; that's how these companies manage "real-time protection". Nobody got hacked by Kaspersky, the NSA contractor didn't follow the regulations he agreed to... specifically the part involving "don't take NSA tech out of the NSA facility, for any reason."