Need a Custom array Index to look up gameobject tags?

I need to create a index of a lot of tags so i can use this to look up these tags very easy.

You may want a hash map like Dictionary in C#. Check it out here:

I assume you want fast lookup from tags to the GameObects with those tags, in which case you probably want something like:

Dictionary<string, List<GameObject>>

Edit: changed GameObject to List

If you want to grab all gameObjects in the scene and add their tags to a List:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class FindTags : MonoBehaviour 
{
	List<string> tags = new List<string>();
	
	void Start()
	{
		foreach(GameObject go in GameObject.FindObjectsOfType (typeof(GameObject)))
			tags.Add (go.tag);
		foreach(string tag in tags)
			print (tag);
	}
}

If you want to name the tags manually:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class TagList : MonoBehaviour 
{
	string[] temp;
	List<string> tags = new List<string>();
	
	void Start()
	{
		temp = new string[]{"Tag1", "Tag2", "Tag3", "Tag4"};	
		tags.AddRange (temp);
		if(tags.Contains(tag))
			print ("This gameObject's tag index is: "+tags.IndexOf(this.tag));
		else
			print ("This gameObject's tag does not exist in your list!");
	}
}