// Instantiates a Plane everytime the game starts and never destroys it
    // even if you stop your game preview
    // NOTE: Watch out, this can cause LEAKS
    function Start() {
        var notDestructable : GameObject = GameObject.CreatePrimitive(PrimitiveType.Plane);
        notDestructable.hideFlags = HideFlags.DontSave;
    }

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Start() {
        GameObject notDestructable = GameObject.CreatePrimitive(PrimitiveType.Plane);
        notDestructable.hideFlags = HideFlags.DontSave;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Start():
        notDestructable as GameObject = GameObject.CreatePrimitive(PrimitiveType.Plane)
        notDestructable.hideFlags = HideFlags.DontSave