Opinions are going far apart from each other here. As far as I know from working for an IT-Security company the safest anti-virus is an intelligent user. Especially in companies it is very important to give introductions for non-IT but also for IT departments for secure passwords, protection against social engineering, data safety and do backups all the time. The anti-virus itself is way less important than these aspects. But if I had to recommend a special software I would suggest Avast. It is lightweight, not annoying and usually doing a good job. Best would be the combination with Little Snitch to watch all network connections.