GameOver.cs

using UnityEngine;
using System.Collections;
using UnityEngine.SceneManagement;

public class GameOver : MonoBehaviour
{
    int score = 0;
    int score2 = 0;
    public GUIElement gui;
    public GUIElement gui2;

    public GUIText myGUIText;
    public GUIText myGUIText2;
    private string scoreVariable;
    private string scoreVariable2;

    // Use this for initialization
    void Start()
    {
        //get our score from playerprefs
        score = PlayerPrefs.GetInt("Score");
        //multiply by 10 as we did on displayed score
        score = score * 10;
        //it is not possible to add P1 and P2 tags to the text, since the GUIText itself uses info from the score
        score2 = PlayerPrefs.GetInt("Score2");
        score2 = score2 * 10;

    }

    void OnGUI()
    {
        myGUIText.text = scoreVariable;
        myGUIText2.text = scoreVariable2;
        //set our text to our score
        scoreVariable = score.ToString();
        scoreVariable2 = score2.ToString();

        //if retry button is pressed load scene 0 the game
        if (GUI.Button(new Rect(Screen.width / 2 - 50, Screen.height / 2 + 155, 100, 40), "Retry?"))
        {
            SceneManager.LoadScene(1);

            //Application.LoadLevel(0);
        }
        //and quit button
        if (GUI.Button(new Rect(Screen.width / 2 - 50, Screen.height / 2 + 205, 100, 40), "Quit"))
        {
            SceneManager.LoadScene(0);
            //Application.Quit();
        }
    }

}

This script creates two GUI buttons to allow the player to retry (thus loading scene 1), or quit (going to scene 0, the loading screen). In addition, it displays the scores that the two players got.