Which of the following tools would be least likely used for stone sculpting?

The use of a screwdriver in stone sculpting is highly unlikely because it is primarily designed for driving screws and not for shaping or carving stone. Stone sculpting typically involves the removal of material from a larger block of stone, which requires tools specifically built for cutting, chiseling, and shaping that material.

Rifflers, chisels, and mallets are essential tools in the sculptor's toolkit, each serving distinct purposes in shaping stone. Rifflers are used for fine detailing and refining the surface of sculptures, chisels are the main tools for cutting into the stone, and mallets are employed to strike chisels, providing the necessary force to remove stone. In contrast, a screwdriver lacks the requisite design and functionality needed for stonework, making it the least relevant tool in this context.