Honestly, I don't use any. I don't get viruses until someone else starts using my computer. The internet, like many other things, just requires good judgement. If you aren't downloading torrents, shady programs, or other *stuff*, you should be fine without.
Though safe commuting is always a good idea, no one is completely safe of viruses. As jefe323 said, you can pick up a virus by simply visiting a website (even if you think it's safe). Why not just download Microsoft Security Essential for free (it's 100% free) to make your computer more secure?
Microsoft Windows Outreach