Which tool is best suited for loosening a rusted bolt?

A breaker bar is the most effective tool for loosening a rusted bolt due to its design that allows for increased leverage. When dealing with rusted or stuck bolts, greater torque is often required to overcome the resistance created by corrosion. A breaker bar is longer than a conventional wrench, providing more leverage and making it easier to apply the necessary force to break the bond of the rust and loosen the bolt.

In contrast, a standard wrench may lack the length required to generate enough torque for particularly stubborn rusted bolts. A torque wrench is designed for precision and is used to apply a specified amount of torque, which is not ideal for loosening rusted fasteners. Lastly, an Allen wrench is typically used for hexagonal socket screws and is not suitable for dealing with rusted bolts in general. The ability of the breaker bar to maximize leverage makes it the best choice for this task.