Rotate player to aim on one axis (Z-axis) towards mouse position/joystick - 2.5D (3D)

I am fairly new to Unity and I am trying to make a game similar to Super Smash Bros. So a 2.5D type of game where plays only move horizontally. I want my players to be spheres with a smaller sphere that rotates 360 degrees around them to aim. Here is an example of what I mean:
Not the best angle, but what I am trying to do is have the green sphere rotate 360 degrees around the other sphere on one axis. I am trying to figure out the best way to do this/ a script to do it. I sort of had a script that would rotate the sphere towards the mouse, but it was glitchy and made the player movement not work well. Then I thought it may be easier to rig up a bone in blender from the center of the sphere out to the smaller "hand" sphere so I could just rotate the bone. I am still having trouble figuring out how to do this/ what the best way to do it is. Like I mentioned above, I want this resemble super smash bros, so there will be multiple people playing at a time so I also want to handle rotating the "hand" with a joystick as well. Any recommendations would be greatly appreciated!
Here is my movement script right now without any rotation code:
`

public class PlayerMovement : MonoBehaviour
{

 public float speed = 10.0F;
 public float jumpSpeed = 13.0F;
 public float gravity = 25.0F;
 public float amount = 10;

 private Vector3 moveDirection = Vector3.zero;
 private CharacterController controller;
 private int jumpCount;
 


 // Use this for initialization
 void Start()
 {
     controller = GetComponent<CharacterController>();
     rb = GetComponent<Rigidbody>();
 }

 // Update is called once per frame
 void Update()
 {

     if (Input.GetButton("Fire1"))
     {
         rb.AddForce(Vector3.back * amount);
         print("clicked");
     }

     if (controller.isGrounded)
     {
         moveDirection = new Vector3(Input.GetAxis("Horizontal"), 0, 0);
         moveDirection = transform.TransformDirection(moveDirection);
         moveDirection *= speed;
         jumpCount = 2;
         if (Input.GetButtonDown("Jump"))
         {
             jumpCount -= 1;
             moveDirection.y = jumpSpeed;
         }
     }

     else
     {
         if (Input.GetButtonDown("Jump") && jumpCount > 0)
         {
             jumpCount -= 1;
             moveDirection.y = jumpSpeed;
         } 
         moveDirection.x = Input.GetAxis("Horizontal") * speed;
     }

     moveDirection.y -= gravity * Time.deltaTime;
     controller.Move(moveDirection * Time.deltaTime);



 }

}