I've tried NOrton, McAfee, PC Cilin, Avast and Zone Alarm.
I say that Zone Alarm is by far the best, it finds every viruses and is very light on memory usage. After ZA I'd pick Avast and PC Cilin.
McAfee was good but this last version full of bugs and uses A LOT of your machine, well and there's is norton which is worse than nothing.