Currently I'm running AVG. As a disclaimer, I'm a AVG reseller (and McAfee for high end data centers) so take my choice with a grain of salt. There are many good A/V providers in the marketplace. Ones that come to mind are: Kaspersky, McAfee, AVG, and even Microsoft Security Essentials. PC Matic looks interesting but I don't have any experience with it.
I'm sure that other members have their favorite protection so don't feel that my list is complete, by any means.