From Unity 4, assuming a default installation directory these templates are found in: C:\Program Files (x86)\Unity\Editor\Data\Resources\ScriptTemplates
In there, you'll find the JavaScript, C# and Boo script templates along with the shader and compute shader templates.
Here's the C# one:
using UnityEngine; using System.Collections; public class #SCRIPTNAME# : MonoBehaviour { // Use this for initialization void Start () { } // Update is called once per frame void Update () { } }