Coup

You hold two face-down character cards and claim to be whoever you want until someone calls you a liar. The action choices are simple: take income, steal coins, or launch a coup to eliminate an opponent's card. If you get caught lying about having the Duke or the Assassin, you lose a life immediately. The rounds take less than ten minutes, making it a fast filler game. It can get exhausting if your friends have predictable tells, though.