Pliers come in an endless variety of shapes and sizes, for a multitude of uses. They are even used in operating theatres and other places where things must be gripped securely. Here we will limit ourselves to pliers that can be put to service in and around the engine.
A pair of pliers to temporarily clamp fuel, brake or coolant lines without damaging or cutting them, for instance. Or a pair of crimping pliers to attach cable lugs and plugs to electrical wire. These may also be equipped with a wire cutter and stripper. Chain riveting pliers to replace your chain yourself may also spark your interest.
There are specific pliers for many specific tasks. With good reason. Most of them can be found here, starting with the ordinary pair of cutting pliers.