I used to use free-av/avira as it only let one virus in after 8 years, but I switched over to avg free for the last 2.
A few other things that I use as well to compliment virus scanners are hijack this, spybot, adaware, and malware bytes. I also use ad block plus (highly recommend) and for the sites I know rely on ad revenue and offer quality services or information, I disable it.
I haven't used microsofts solution, but I hear nothing but good things. I've had bad experiences with Norton, and I've had mediocre experiences with mcafee on an enterprise level, but I'm not fond of their personal user software.
A lot of these I haven't heard of, so I may have to set up a few vm's and give them a thorough testing to see if there's one that I like better than avg :D