Homing Missiles!

Here's the code I created for a missile.

 using UnityEngine;
 using System.Collections;
 
 public class Missile : MonoBehaviour {
     public float RangeTilShutdown;
     public int DamageToShields;
     public int DamageToHull;
     public GameObject ExplosionSmall;
     public Vector3 PositionSpawned;
     private GameObject[] Flares;
     private GameObject[] Hostiles;
     private GameObject MissileTarget;
     private bool Ready = false;
 
     void Start () {
         PositionSpawned = gameObject.transform.position;
         Flares = GameObject.FindGameObjectsWithTag ("Flare");
         Hostiles = GameObject.FindGameObjectsWithTag ("Hostile");
         if (Flares.Length > 0) {
             MissileTarget = Flares [0];
         } else if (Hostiles.Length > 0) {
             MissileTarget = Hostiles [0];
         }
     }
 
     void Update () {
         if (MissileTarget != null) {
             GetComponent<SlerpToLookAt> ().Target = MissileTarget.transform;
         } else {
             Destroy (gameObject);
         }
         if (Vector3.Distance (gameObject.transform.position, PositionSpawned) >= RangeTilShutdown) {
             Destroy (gameObject);
         }
     }
 
     void OnCollisionEnter(Collision Other) {
         ContactPoint Contact = Other.contacts [0];
         Quaternion Rot = Quaternion.FromToRotation (Vector3.up, Contact.normal);
         Vector3 Pos = Contact.point;
         Instantiate (ExplosionSmall, Pos, Rot);
         if (Other.gameObject.GetComponent<Shield> ().ComponentDisabled == false) {
             int TargetDamageVariance = Other.gameObject.GetComponent<Shield> ().DamageVariance;
             int DamageDealt = DamageToShields + Mathf.RoundToInt(Random.Range(-TargetDamageVariance, TargetDamageVariance));
             Other.gameObject.GetComponent<Shield> ().Power -= DamageDealt;
         } else if (Other.gameObject.GetComponent<HullIntegrity> ().ComponentDisabled == false) {
             int TargetDamageVariance = Other.gameObject.GetComponent<HullIntegrity> ().DamageVariance;
             int DamageDealt = DamageToHull + Mathf.RoundToInt (Random.Range (-TargetDamageVariance, TargetDamageVariance));
             Other.gameObject.GetComponent<HullIntegrity> ().Integrity -= DamageDealt;
         }
         Destroy (gameObject);
     }
 }
 

This is SlerpToLookAt.cs:

 using UnityEngine;
 using System.Collections;
 
 public class SlerpToLookAt: MonoBehaviour {
     public Transform Target;
     public float RotationSpeed;
 
     private Quaternion _LookRotation;
     private Vector3 _Direction;
 
     void Update () {
         _Direction = (Target.position - transform.position).normalized;
         _LookRotation = Quaternion.LookRotation (_Direction);
         gameObject.transform.rotation = Quaternion.Slerp (transform.rotation, _LookRotation, Time.deltaTime * RotationSpeed);
     }
 }

Be sure to also attach SlerpToLookAt.cs onto the missile. Also attach rigidbody and constant force. On rigidbody, uncheck "Use Gravity". On constant force, put the speed desired in the z axis of relative force. By the way, the flares gameobject[] is for antimissile flares. You can remove that if you want. I used this for a 3D game, but it probably can also work in 2D.