I currently carry a CRKT Longs Peak. It's a nice little tac folder without a serrated edge (I'm not a fan of them because, although they cut better, they're hard to sharpen). It's also got a dual lock feature so that there is no possibility of the blade closing in on your fingers.
Of course, if we're talking about favorite knives, I'll always swear by my Ka-Bar. Those leathernecks really know how to design a knife.