Depends the kind of protection you want, Malware or Regular Antivirus? For windows really is defender, usually you won't need anything else if you know how to navigate the web and be safe. Avast! Is one that I always go to if someone asks, there is also AVG though I heard it consumes a bit more of resources, not sure. For malware there is Malware-Bytes. These are the two usual go to for regular users.