It's stretching the definition of "political speech" considerably, and may not have happened in this form in real life, but the version of Taira no Kiyomori's last words recorded in the Tale of the Heike is pretty badass:
Build no halls or pagodas after I die; dedicate no pious works. Dispatch the punitive force immediately, decapitate Yoritomo, and hang his head in front of my grave. That is all the dedication I require.
The Appeal of 18 June and the "finest hour" speech--delivered on the same day!--are also both pretty amazing, and the Gettysburg Address goes without saying.