I run nothing on my personal devices / workstations. Ten years ago I gobbled together a service similar to VirusTotal, but it was a real pain to keep that working. I used to to test suspicious files.
As for not running anything it leaves me only insecure to actual worms who replicate through 0days where somebody performs scans and may hit me, if there's a vulnerability in any of my system's software, or in the OS itself. But so far, nothing.
A bit of common sense and being "paranoid" works good enough for me. If I must run something and I cannot analyse via hex editing (to see if there is anything suspicious), then it goes into a sandbox and I observe how it behaves. Most AVs are a joke and are incredibly easy to circumvent, particularly Norton Anti-Virus (or whatever they call it today).
...but I must admit, I did install Comodo on the laptop as my niece uses it frequently so it is prone to getting odd files and malware onto it. So at least that hinders some of it. But on my other devices, such as my workstations, they're only a resource hog and I just don't need it. You, that is, yourself, is probably the best AV — if you know the ins-and-outs of your system. -_-
Just my nine shekels.
