Which tool is primarily used to achieve an unshaven appearance?

The correct choice of stipple sponge is rooted in its specific design and purpose for makeup application. A stipple sponge is characterized by its unique texture, which allows for the application of products in a way that mimics natural skin irregularities. This tool is particularly effective for achieving an unshaven look, as it can create a layered effect by allowing products like cream or foundation to be applied in a blotchy or uneven manner. This results in a realistic portrayal of stubble or facial hair growth, which is essential for theatrical performances or certain character looks.

In contrast, other tools like a foundation brush and make-up sponge are primarily intended for smoothing out makeup for an even finish, which would not align with the aim of creating a scruffy or unshaven texture. A wax applicator is typically used for applying wax products, which may not contribute effectively to the intended unshaven appearance. Therefore, the stipple sponge stands out as the best tool for achieving this specific effect due to its ability to create texture and depth in makeup application.