This is the last full week of shows for Late Show with David Letterman (the final three installments are presented next week, and will take us through the end of the May sweeps ratings period Wednesday night). The guests tend to get more special, at least for Dave, as the nights count down, and tonight’s guests are two of his long-time favorites, and fellow Dispensers of Outraged and Outrageous Honesty: Howard Stern and Don Rickles. Here’s hoping Letterman persuades them to appear at the same time…