For me, Klonopin. A benzo like valium but with an intermediate half-life. Puts me right out and doesn't leave me groggy like valium. Ambien is a good choice as well, but it's not quite as effective for me as klonopin. Xanax will work also, but it's a short half-life, you're likely to wake up in the middle of the night when it wears off.