I use ClamTK as AntiVirus, it updates everyday as a daemon and I scan twice a month.
As for Firewall, I used to use Firestarter but it has a bug in most of the latest debain distributions which doesn't output a real-time connection list.
And because Firestarter has stopped production and support, I doubt it will ever be fixed unless a patch is released.

I sometimes use UFW, but I don't need to use the GUI because it runs on startup anyway, if I need to port forward, I'll do it in the terminal.

IPTables.. I don't have enough knowledge yet :P