Followed this official tutorial, my own version on GitHub, and you can see it in action here (WSAD to move, mouse click to shoot).

Steps on how to create this:

Create a new 3D project
Save the scene as Main
Create -> 3D object -> Plane
Create -> 3D object -> Cube
1. Add Component -> Physics -> Box collider
2. Add Component -> Physics -> Rigidbody
3. Drag and drop this object in the Assets/Prefabs folder
4. Make duplicates (use snapping to move by using the ctrl key)
5. Make a row of them (about 8) and then make a new empty object and drag them all into this object
6. Now duplicate this object and position above (again by using snapping with ctrl key)
Create -> 3D object -> Sphere
1. Add Component -> Physics -> Sphere collider
2. Add Component -> Physics -> Rigidbody
3. Make it into a prefab
4. Delete it from Hierarchy

On the camera object => Add Component -> Script:

#pragma strict

public var projectile : Rigidbody;
public var shotPos : Transform;
public var shotForce : float = 1000f;
public var moveSpeed : float = 10f;

function Update ()
{
    var h : float = Input.GetAxis("Horizontal") * Time.deltaTime * moveSpeed;
    var v : float = Input.GetAxis("Vertical") * Time.deltaTime * moveSpeed;
    
    transform.Translate(new Vector3(h, v, 0f));
    
    if(Input.GetButtonUp("Fire1"))
    {
        var shot : Rigidbody = Instantiate(projectile, shotPos.position, shotPos.rotation);
        shot.AddForce(shotPos.forward * shotForce);
    }
}

Drag the Sphere prefab to the projectile.

Create empty game object and rename to shotPos.
1. Drag and drop it on the camera
2. Reset transform origin
3. Position y=-0.5, z=1
4. Rotation x=-15
Drag Camera to shot pos variable in the script.
If you want to clean up the bullets after 2 seconds, add script to Sphere prefab:
```
function Start () {
	Destroy(gameObject, 2f);
}
```

Unity3D Brick Shooter