var other : GameObject;
other.guiText.text = "HelloWorld";

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
public GameObject other;
void Awake() {
other.guiText.text = "HelloWorld";
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

public other as GameObject

def Awake():
other.guiText.text = 'HelloWorld'