ProtectMac has everything you need in a virus protection program. It can run scans of your whole computer or individual files. It can run scheduled background scans or you can do it manually whenever the mood strikes you. However, I think the best feature is the Trojan detection. Macs aren't vulnerable to many viruses yet, but Trojans can be hidden in spam and leech off of your computer (or turn it into a spam bot without you knowing. The horror!) or phish for your passwords or credit card numbers (more horror!). ProtectMac detects and destroys Trojans with a simple click of the mouse.
I ran it over my whole MacBook. It took about two hours to scan everything, and when it was done I had one Trojan in an unopened piece of spam. ProtectMac got rid of it (I just had to click Delete), and I haven't had a problem since.