I personally prefer old exposed hammer actions, so my choice would be one of those. My favorite isn't one I'd classify as "best" as it's the Marlin Ballard action. I love the design, the look, and the feel of the Ballard.
But if I was building up an action for a ground up do most anything single shot rifle, I'd buy an MVA High Wall action. They're strong enough for anything I'd want to build, and have double set trigger options, as well as pistol grip tang options. A guy could make a strong, beautiful single shot hunting, or target rifle on the MVA action.