Which tool requires regular sharpening to maintain its effectiveness?

The straight razor is the tool that requires regular sharpening to maintain its effectiveness. This is because the blade of a straight razor is designed for precision cutting, and a sharp edge is crucial for achieving clean, smooth shaves. Over time and usage, the edge can become dull, which necessitates honing or stropping to restore its sharpness. This regular maintenance is essential for both the performance of the tool and the safety of the user, as a dull razor can lead to nicks and less effective cutting.

In contrast, tools like safety scissors are designed to maintain a sharp edge for longer periods without frequent sharpening due to their construction and intended use. Electric clippers use blades that may need occasional cleaning and oiling, but not regular sharpening in the same way a straight razor does. Lastly, combs do not have blades and therefore do not require sharpening at all. In this context, the need for regular sharpening clearly identifies the straight razor as the correct choice.