Well speaking very quietly, I use Norton at home (a cracked version so i don't have to pay)

It is definitely a memory sucker, but it's never done me wrong.
At work we use "AVG Free Edition", which after using it I'm rather impressed. I just looked it up and after reading the fine print, it is illegally installed there because it is ment for non-commerical environment. I would say, it is everything the home user needs.