Someone (Guest!) suggested Niel (sp) Gow's Lament for the Death of his Second Wife: it is a fabulous tune, but although a slow air, is definitely not for beginners.
It requires a certain maturity of playing to do it justice, and can be totally murdered when you get a mass of people in a session trying to all play it together. Strictly for advanced players with plenty of expression. dynamics, etc: not for beginners.