There used to be a time when Comodo was said to be really good. Any user around?

Have a look around this site:

http://www.techsupportalert.com/

They are pretty good at keeping upto date on what's hot or not etc

I use Comodo, had to uninstall when I wanted to play LA Noire (deactivating didn't help only uninstalling it)
Recently switched back and no complaints so far.

I use Avira and Avast on different machines. I like them both, mostly. And MalwareBytes is always good.

A lot is about preference and trust. Which for me means no McAfee, Norton, Avast or AVG. All because of personal experiences on either my own pc or on that of family. Though I have to say that's all been 10-15 years ago.
Norton (2003 IIR) was late with definitions for Netsky.P. As a result a lot of Norton users, my parents included, got infected.
Before that I had an infection on an up-to-date McAfee protected pc. That infection was even worse as the virus was around half a year old. IIRC correctly it came from opening a file from inside a zip archive.
After those 2 I used AVG and later Avast. Again, this is at least 10 years ago, but in those days I wouldn't even have called them a security product. They were very bad. Both let a lot of stuff through, especially from e-mails, archived files and infected websites.

I know McAfee was purchased by Intel. No idea if there are any consequences when it comes to quality. We use it at work, but several colleagues regularly have infections on their pc.
From what I've heared and read, Symantec got there act together when it came to Norton. No idea if it's good and user friendly now, but I know it's better than it was in the 1st years of the previous decade.
Avast I don't know much about nowadays, except that it's free.
AVG seems to have regular false positives, especially on Windows system files.

Personally I've chosen for a product which is in the top of various tests every year, GDATA. If I wouldn't have chosen that 1, I would probably have chosen BitDefender or Kaspersky. Quality wise I'm happy with GDATA. The firewall could be more user friendly. Blocking programs is too much manual labour.

Knowing Avast and AVG usually end up as average in tests and Microsoft Security Essentials ending at the bottom, I'm wondering how people know their pc is still clean. Do you use a webscan on sites like BitDefender? Your AV not finding anything or not giving any warnings, doesn't mean your system is clean.

I occasionally scan online. Except for GDATA, I also have a registered version of Malware Bytes Antimalware. On top of that I use Spybot Search & Destroy and SpywareBlaster. As a browser I use Pale Moon with the Adblock Edge and Ghostery add-on.

There's also <span class="bold">VirusTotal</span>, a website service now owned by Google, where you can submit files and scan them for viruses. It uses 61 different antiviruses and scan engines, which makes it very good for spotting any false positive. VirusTotal can also analyze any website's URL you provide, to see if it contains any malicious script or download link.

Stuxnet

Only execute code you compiled yourself and after the initial installation never connect to the Internet again.

Another vote for the Malwarebytes/Avast combo. Works for me.

Since I'm on Windows 8.1, I have the default one (Windows Defender, which is a renamed Security Essentials) + Malwarebytes + Adblock (yes, some ads are too well designed and drive people to malware sites).

For the people using Avast, it was involved in a spying scandal, their makers now claim they stopped doing such actions, but I wouldn't trust them, they were doing that in the shadows during several years until someone discovered it and can do that again.

Best free virus? Hmm... that should be relatively easy to catch and to infect your system by simply surfing the web and opening dubious attachments. :D

Kidding! I'd vouch for Malwarebytes and maybe AVG.

I still use Comodo internet security and Malwarebytes.

Until now, Comodo has always managed to detect and keep my systems free from nasties, while Malwarebytes is my absolute favorite to clean out already infected machines.

A comparison of various anti-virus and firewalls:

http://www.matousec.com/projects/proactive-security-challenge/results.php
http://www.matousec.com/projects/proactive-security-challenge-64/results.php

It is all you'll ever need

Trojan Horse is an oldie but a goodie.