Trigger animation when looking at an object?

You probably want something like this:

 RaycastHit hitInfo;
 Ray ray = new Ray(transform.position, transform.forward);
 bool didRayHit = Physics.Raycast(ray, out hitInfo, 10f);
 if (didRayHit)
 {
     print("I am a 10 unit long ray hitting " + hitInfo.transform.name);
     //hitInfo.doAnimationStuffHere;
 }

the float 10 in the physics.raycast is the length of the ray. change it to any float value to change the length of the ray.