AVG here, much thanks to Ord. (Thank you Ord!)
I had Norton on my old laptop, but I never paid for it. I don't know if it was an older free version or what, but I never worried about it. I never got a virus on my old laptop, although I don't remember it doing much either.
My parents have MacAfee on theirs, but it came free with their internet service. It seems to work well, too.