MonoBehaviour.OnMouseDown()
Description

OnMouseDown is called when the user has pressed the mouse button while over the GUIElement or Collider.

This event is sent to all scripts of the Collider or GUIElement.
	// Loads the level named "SomeLevel" as a response
	// to the user clicking on the object

function OnMouseDown () { Application.LoadLevel ("SomeLevel"); }
This function is not called on objects that belong to Ignore Raycast layer.

OnMouseDown can be a co-routine, simply use the yield statement in the function. This event is sent to all scripts attached to the Collider or GUIElement.