Which component is necessary for a GameObject to participate in collision detection?

For a GameObject to participate in collision detection in Unity, it is essential to have a Collider component attached to it. The Collider defines the shape of the GameObject's physical boundary that can interact with other colliders. When two GameObjects with colliders overlap, Unity can detect this interaction and respond accordingly, whether that means triggering events, applying physics effects, or initiating gameplay mechanics.

While a Rigidbody is also significant for enabling physics interactions, particularly for dynamic objects that respond to forces, the presence of a Collider is the fundamental requirement for collision detection. A Renderer is primarily concerned with the visual representation of the GameObject and does not influence collision physics. Similarly, scripts can be used to manage behaviors or logic but do not inherently allow for collision detection themselves. Thus, having a Collider is the core requirement for any GameObject to participate in collision detection within the Unity physics system.