The other collider in contact.

	// Prints the name of the collider this transform collided with
	function OnCollisionEnter(other : Collision) { 
		print("This collider collided with: " + other.contacts[0].otherCollider.name);
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnCollisionEnter(Collision other) {
        print("This collider collided with: " + other.contacts[0].otherCollider.name);
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnCollisionEnter(other as Collision) as void:
		print(('This collider collided with: ' + other.contacts[0].otherCollider.name))