Psuedo: Have an array of sounds... Or a List as people here like more.. W/e it's the same.

Get a random number in the array, each array spot has its own sound, so if you have 10, get a number between 1 and 10, and then play that when you kill someone... That make sense? So every kill, it gets a new number, which is a "new" sound...

Try this it works for me :

      using UnityEngine;
using System.Collections;

public class PlayMusic : MonoBehaviour {



    public AudioClip[] Tracks;

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


            if (GUI.Button(new Rect(10,20,120,20),"Play Tracks")){
                audio.Stop();
                audio.PlayOneShot(Tracks[Random.Range(3,Tracks.Length)]);
                //audio.clip = Tracks[0];
                   //    audio.Play();
            }

        }
    }

it was similar to Fierce Waffle answer mines basically plays when you click on the GUI button :)

I would go with a random number generating system and have different voices for different numbers. I'm not exactly and expert when it comes to random generating but I got the idea from DOS. How in dos many games were random. but here's a little snip it of what

create an audio array. and pretend your when your player dies you call this function

function playDeathSound()
{
deathSounds.Play[Random.Range(0, deathSounds.length)]();
}