Heres a Script for SloMo hold left shift

using UnityEngine; using System.Collections;

public class ShiftForSloMo : MonoBehaviour {

public int SetSlomoSpeed = 0;

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {

    if(Input.GetKeyDown(KeyCode.LeftShift))
    Time.timeScale = SetSlomoSpeed + .3f;

    if(Input.GetKeyUp(KeyCode.LeftShift))
        Time.timeScale = 1f; 
}

}

There is a place for this stuff on the wiki:

http://www.unifycommunity.com/wiki/index.php?title=Scripts

JS FIXED

#pragma strict

var SetSlomoSpeed : int = 0;

function Start () {

}

function Update () {
if(Input.GetKeyDown(KeyCode.LeftShift)){
Time.timeScale = SetSlomoSpeed + .3f;
}
else{
if(Input.GetKeyUp(KeyCode.LeftShift)){
Time.timeScale = 1f;
}
}
}