I have AVG Free version. Although that's getting rather naggy recently and wanting to install toolbars and link 'protection' (and the paid version of course), and isn't as light as it used to be. But at least it uninstalls cleanly. I did try one of the other ones (Avast or Avira, I unremember which because the names are similar) but it seemed more intrusive. But I might give it/them another try if AVG annoys me some more.