Marital Rape
Can a man rape his wife? Should the punishment be less if you assume he can? What does rape constitute within marriage? Is unwanted sex while sleeping rape? If so, can a woman rape her husband? Should these prosecutions occur without the consent of the spouse? If so, why?

Here's a bit of an intro into the debate, although a lexis nexis search (or alternatively a google search) on marital rape laws will give you much more.