Mike Stevenson's shufflebag helper class

ShuffleBag.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class ShuffleBag<T> : ICollection<T>, IList<T>
{
  private List<T> data = new List<T> ();
	private int cursor = -1;
	private T last;

	public ShuffleBag ()
	{
	}

	public ShuffleBag (IEnumerable<T> contents)
	{
		foreach (var item in contents) {
			Add (item);
		}
		cursor = -1;
	}

	public T Next ()
	{
		if (cursor < 1) {
			cursor = data.Count - 1;
			if (data.Count < 1)
				return default(T);
			last = data [0];
			return data [0];
		}
		T temp;
		do {
			int grab = Mathf.FloorToInt (Random.value * (cursor + 1));
			temp = data [grab];
			data [grab] = data [cursor];
			data [cursor] = temp;
			cursor--;
		} while (last.Equals (temp) && data.Count > 1);
		last = temp;
		return temp;
	}


	#region IList[T] implementation
	public int IndexOf (T item)
	{
		return data.IndexOf (item);
	}

	public void Insert (int index, T item)
	{
		data.Insert (index, item);
	}

	public void RemoveAt (int index)
	{
		data.RemoveAt (index);
	}

	public T this[int index] {
		get {
			return data [index];
		}
		set {
			data [index] = value;
		}
	}
	#endregion



	#region IEnumerable[T] implementation
	IEnumerator<T> IEnumerable<T>.GetEnumerator ()
	{
		return data.GetEnumerator ();
	}
	#endregion

	#region ICollection[T] implementation
	public void Add (T item)
	{
		data.Add (item);
		cursor = data.Count - 1;
	}
	
	public int Count {
		get {
			return data.Count;
		}
	}

	public void Clear ()
	{
		data.Clear ();
	}

	public bool Contains (T item)
	{
		return data.Contains (item);
	}

	public void CopyTo (T[] array, int arrayIndex)
	{
		foreach (T item in data) {
			array.SetValue (item, arrayIndex);
			arrayIndex = arrayIndex + 1;
		}
	}

	public bool Remove (T item)
	{
		return data.Remove (item);
	}

	public bool IsReadOnly {
		get {
			return false;
		}
	}
	#endregion

	#region IEnumerable implementation
	IEnumerator IEnumerable.GetEnumerator ()
	{
		return data.GetEnumerator ();
	}
	#endregion


}