rotate towards player in one axis

gistfile1.txt

// lookat with fixed transform flipping in certain angles:
transform.LookAt(target, transform.up);

LookTowardsPlayerOneAxis.cs

using UnityEngine;
public class LookTowardsPlayerOneAxis : MonoBehaviour
{
    public Transform target;
    void LateUpdate()
    {
        // note Y position is set to current
        Vector3 targetPos = new Vector3(target.position.x, transform.position.y, target.position.z);
        transform.LookAt(2 * transform.position - targetPos);
    }
}