False Flag - Use your own spies to carry out an attack upon your own civilization/federation (gaining a CB) and declare war upon the civilization/federation you framed for the attack.
Game of Galactic Thrones - As a monarchy, PU another monarchy.
The Rumors of My Death Have Been Greatly Exaggerated - Another nation assassinates your leader, yet because you have a cloning policy, your leader doesn't "die".
More will come...