ControllerColliderHit.point  

// print the point we impacted
function OnControllerColliderHit(hit : ControllerColliderHit) {
    Debug.Log("I impacted at: " + hit.point);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void OnControllerColliderHit(ControllerColliderHit hit) {
        Debug.Log("I impacted at: " + hit.point);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def OnControllerColliderHit(hit as ControllerColliderHit):
        Debug.Log(('I impacted at: ' + hit.point))