Awesome

UnityObjectPooler

Simple object pool for Unity

This is a quick and lightweight solution that you can just immediately throw objects at to be pooled. (.Net 4.6+)

• No need to pre-define pools (although you can if you want).
• Calls Spawn/Despawn interface
• Neatly organized in project hierarchy

Instantiating objects (taking them from the pool):

var obj = ObjectPooler.Instance.Spawn(prefab, position, rotation);

Destroying objects (adding them back into the pool):

ObjectPooler.Instance.Despawn(gameObject);   

Preparing objects for re-use.

public class Enemy : MonoBehaviour, IPoolable
{
    public void Spawn()
    {
        // do stuff...
    }

    public void Despawn()
    {
        // do stuff...
    }
}