Which type of knife is best for cutting through tough food items such as squash?

The cleaver is particularly well-suited for cutting through tough food items like squash due to its design and construction. With its large, heavy blade, a cleaver provides the necessary weight and force to break through hard surfaces. The blade's thickness also contributes to its ability to handle denser produce without bending or breaking.

In contrast, while a chef’s knife is versatile and can handle many tasks, its thinner blade is not as effective for very tough items. A paring knife is designed for intricate tasks such as peeling and trimming, making it impractical for cutting through something as sturdy as squash. A fillet knife, designed for removing bones from fish, has a flexible, thin blade that would not provide the necessary leverage or power required to slice through tougher vegetables. Therefore, for tough items like squash, the cleaver is the most effective and appropriate choice among the options.