You can try using public static. Just attach them to the script and call them with the script's name. Then attach the script to a GameObject that can persist throughout all levels.

something like this.

In Javascript named "AppConfig"

static var myVar:int = 10;

In all other scripts you can call it in this manner: AppConfig.myVar

To allow it to persist in all scenes apply this on the GameObject the script is attached to:

// Make this game object and all its transform children
// survive when loading a new scene.
function Awake () {
DontDestroyOnLoad (transform.gameObject);
}

Any public variable can be accessed from any object; see here. It's generally best not to use static variables unless you have a reason for it, since they have certain limitations (see the 6th post in this topic for a discussion of these), although a player's score is probably a good candidate. Only one scene at a time can be loaded, but you can use DontDestroyOnLoad in order to persist manager scripts across scenes. You can save and load variables using PlayerPrefs.