If you want to make a point, a deliberately-staged temper tantrum might fit the bill. What makes this effective is that it is unexpected. If done sparingly, you can show that you mean business. Having a temper tantrum can also backfire. If a negotiation is particularly volatile and the parties are already discourteous and rude, a temper tantrum is not going to stand out.
If you do get angry, it should be on purpose and for effect as though you were an actor in a play. Generally it is better to be polite and charming, but not too charming or you will seem insincere. If you get angry and it is not staged, then you will be out of control. As Shakespeare said in As You Like It., ” All the world is a stage and all the men and women merely players.”
The whole negotiation process is acting to some degree. You don’t want the other side to know what your position is and how you really feel. However, on rare occasions, you may feel that the timing is right to show anger. Just make sure you are acting and in control.
Here is an example. When you are told your reserved hotel room has been given to someone else, that controlled anger may be a way to get the hotel’s attention since they generally won’t want you to make a scene. One the other hand, you are always taking a chance that you will humiliate yourself. It is best to try this when you have nothing to lose and may never see this person again. If you go forward, prepare your script and practice just as an actor would do. Give details so the person knows why you are so upset. Since you are in control, don’t go overboard with your performance. When you stage a scene like this, always end with a proposed solution. Otherwise your performance may be wasted and the other party may not feel like proposing a solution after you have yelled at them.