Junta is good. Alas, I never played, only watched people play it on a Diplomacy convention. Too bad it takes nearly as long as Diplomacy.

If you want to lose your friends more quickly, you should try Kuhhandel (http://www.boardgamegeek.com/boardgame/1117). That's poor evil `attacking', bluffing and second-guessing. (Unfortunately alliance are not common, so you do not get to break your word and stab your friends. But still a good game. :)