Transform.forward  

// Set's the rigidbody velocity to be
// along the blue axis of the transform

rigidbody.velocity = transform.forward * 10;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
rigidbody.velocity = transform.forward * 10;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
rigidbody.velocity = (transform.forward * 10)

// Computes the angle between the target transform and this object
var angleBetween = 0.0;
var target : Transform;
function Update () {
var targetDir = target.position - transform.position;
angleBetween = Vector3.Angle (transform.forward, targetDir);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
public float angleBetween = 0.0F;
public Transform target;
void Update() {
Vector3 targetDir = target.position - transform.position;
angleBetween = Vector3.Angle(transform.forward, targetDir);
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

public angleBetween as single = 0.0F

public target as Transform

def Update():
targetDir as Vector3 = (target.position - transform.position)
angleBetween = Vector3.Angle(transform.forward, targetDir)