Hey, I am currently working on a Space Soccer Game and their Ai at the moment. You can check out my current progress here: http://pixelpizza.de/unity/football_ai.html the controls are A and D to move and W for a special attack.
as you can see, the Drone is just following the Ball but i want to switch between a Defensive and Offensive behavior. so that the Drone is pushing the Ball to the Goal and also moving back to his own goal when the player is near the own goal. the Ai code looks like this atm:
using UnityEngine;
using System.Collections;
public class DroneBehavior : MonoBehaviour {
private GameObject player;
[SerializeField]
private float moveSpeed = 250;
[SerializeField]
private float minDistance = 50.0f;
[SerializeField]
private float maxDistance = 100.0f;
[SerializeField]
private float rotationDrag = 0.75f;
[SerializeField]
private bool canShoot = true;
[SerializeField]
private float brakeForce = 5f;
private bool isShooting = false;
private Vector3 direction;
private float distance = 0.0f;
public enum CurrentState { Idle, Following, Attacking };
public CurrentState currentState;
public bool debugGizmo = true;
public float DistanceToPlayer { get { return distance; } }
public bool CanShoot { get { return canShoot; } set { canShoot = value; } }
void Start()
{
player = GameObject.FindGameObjectWithTag("Ball");
currentState = CurrentState.Idle;
isShooting = false;
}
void Update()
{
//Find the distance to the player
distance = Vector3.Distance(player.transform.position, this.transform.position);
//Face the drone to the player
direction = (player.transform.position - this.transform.position);
direction.Normalize();
}
private void FixedUpdate()
{
this.GetComponent<Rigidbody>().rotation = Quaternion.LookRotation(direction, Vector3.up);
this.GetComponent<Rigidbody>().angularDrag = rotationDrag;
//If the player is in range move towards
if(distance > minDistance && distance < maxDistance )
{
currentState = CurrentState.Following;
DroneMovesToPlayer();
}
//If the player is close enough shoot
else if(distance < minDistance)
{
DroneStopsMoving();
if(canShoot)
{
currentState = CurrentState.Attacking;
ShootPlayer();
}
}
//If the player is out of range stop moving
else
{
currentState = CurrentState.Idle;
DroneStopsMoving();
}
}
private void DroneStopsMoving()
{
isShooting = false;
this.GetComponent<Rigidbody>().drag = (brakeForce);
}
private void DroneMovesToPlayer()
{
isShooting = false;
//this.GetComponent<Rigidbody>().AddForce(-200,200,0);
this.GetComponent<Rigidbody>().AddRelativeForce(Vector3.forward * moveSpeed);
}
private void ShootPlayer()
{
isShooting = true;
//Shoot player ...
}
private void OnDrawGizmosSelected()
{
if (debugGizmo)
{
Gizmos.color = Color.green;
Gizmos.DrawWireSphere(this.transform.position, maxDistance);
Gizmos.color = Color.red;
Gizmos.DrawWireSphere(this.transform.position, minDistance);
}
}
}
maybe someone has a great idea how to do this 
thanks!