Not really. That's what your firewall is for, to stop intruders.
Very true, firewalls are essential even if you believe that you won't be attacked.
AV software is a form of protection while you browse the WWW. And most viruses have to be activated by the user anyway; by opening up files in emails and downloaded files.
If you're an outlook user, the active AV software is a very good idea as most of the attachments are opened (in some versions of outlook) when downloaded so the active virus scanning is a VERY good idea.
Kind of like the 'guide dog for the blind'.
I wouldn't call myself blind, I would say it's more personal preference, I could live without AV software as I know what I'm clicking on and know what sites to allow activeX controllers on, or download from. However, I still choose to have AV software.
Edit: I mainly choose Comodo AV due to it's ability to stop any programs from running or accessing system resources until I give the go ahead, that way if I do download a program that I'm unsure about, I can sandbox it or not allow access to certain system resources.