Bitdefender on the Mac App Store
MalwareBytes has a Mac version, I can only guess it should be the next runner up
Kapersky on the Mac App Store when it was free, since then it has upped to 12 bucks for the full version (no subscription). no link because it's not free
ClamXAV but cannot recommend as I had a hacking tools disk in my computer and copied the files to my computer, it should have recognized them as trojans, spyware, and worms but it only found 2 of nearly 30 tools so I'm just going to say no.
Maybe AVG, but it's pretty bloated, while it performs a fairly quick full scan, relative to others, and offers a lot more features than Bitdefender, the performance hit is noticeable when doing other things.
Trend also has an antivirus solution but they got popped for security holes in their own protection software so I pass on their stuff.
As with anything, if you've never heard of the software, don't download it, if you feel like you really need it, do some quick 5 minute research on it, don't go off the first article you read, instead take an average, and if the website is bloated with ads or looks very similar to another that you just visited (taboola websites), don't trust it.
Ads are one of the biggest reasons for malware because of the big green download buttons (see cnet.com's download area). Instead of running ad blocking software I just download a hosts file and block them that way. The website I'm going to link you to looks sketchy (and dated) but I use this same hosts file. All you are interested in is the stuff under localhost 127.0.0.1 and the IPV6 version of that. It should start where it says # [Start....]. Just copy that line and everything below it into your own hosts file below your own localhost entry. It is constantly updated to include the newest stuff. But it should work well for some time. It isn't an end-all to ads but it helps. Even though it says for Windows, it works on Mac.
Anyways here's the link:
http://winhelp2002.mvps.org/hosts.htm
For Windows you'll want to paste the selection into the hosts file (admin needed) located at C:\Windows\System32\drivers\etc\hosts
For Mac and Linux it's even easier
/etc/hosts
The "hosts" at the end is the actual file. If you run into any issues with websites, you have two options 1) restore the hosts file (might make a backup) or 2) guess which entry it is by either removing a selection at a time until the page works correctly, then narrow it down by pasting selections back in (brute force way) or you can view the page source (right click menu on the webpage) and try to figure out what the page is requiring, search for it in the hosts file and remove the entry one at a time.