GameObject obj = GameObject.Find ("オブジェクト名");

GameObject Packman = GameObject.Find ("PackMan");

GameObject.Find ("Score").GetComponent<GUIText> ().text = "テキスト内容";

if(collision.gameObject.CompareTag("Enemy")){
	Object.Destroy(gameObject);
}

GameObject[] objs = GameObject.FindGameObjectWithTag ("タグ名");

GameObject[] objs = GameObject.FindGameObjectWithTag ("Sphere");
	foreach (GameObject obj in objs) {
		if (obj.name != "Sphere") {
			Color c = obj.GetComponent<Renderer> ().material.color;
			c.a = 0.5f;
			obj.GetComponent<Renderer> ().material.color = c;
			obj.GetComponent<Renderer> ().material.shader= Shader.Find ("GUI/Text Shader");
		}
	}