Two extension methods that make it really easy to grab a random element from a list. You will need to update `RandomService.Random` with a global RNG.

RandomFromList.cs

public static class CollectionExtensions
{

    /// <summary>
    /// A Linq-like method for getting a random element from an IEnumerable
    /// </summary>
    /// <typeparam name="T">The element type</typeparam>
    /// <param name="array">The array to fetch an element from</param>
    /// <param name="rand">Optional Random instance, if not provided 
    /// the method will use the RandomService.</param>
    /// <returns>An element of type T or default(T)</returns>
    public static T Random<T>(this IEnumerable<T> enumerable, Random rand = null)
    {
        rand = rand ?? RandomService.Random;
        T o;
        var c = enumerable.Count();
        if (c > 0)
        {
            o = enumerable.ElementAt(rand.Next(0, c));
        }
        else
        {
            o = default(T);
        }
        return o;
    }

    /// <summary>
    /// A Linq-like method for getting a random element from an array
    /// </summary>
    /// <typeparam name="T">The element type</typeparam>
    /// <param name="array">The array to fetch an element from</param>
    /// <param name="rand">Optional Random instance, if not provided 
    /// the method will use a static default instance.</param>
    /// <returns>An element of type T or default(T)</returns>
    public static T Random<T>(this Array array, Random rand = null)
    {
        rand = rand ?? RandomService.Random;
        T o;
        var c = array.Length;
        if (c > 0)
        {
            try
            {
                o = (T)array.GetValue(rand.Next(0, c));
            }
            catch
            {
                o = default(T);
            }
        }
        else
        {
            o = default(T);
        }
        return o;
    }
}