This piece of promotion technique was done by Western Union as part of their fund raising efforts for Tsunami victims in Sri Lanka. A piggy bank in the shape of Sri Lanka was made and was filled with water. The more coins people put in the container, more water is pushed out through the duct in the container, eventually making the container water free or Sri Lanka, Tsunami water free. Don't ask me what will happen to the currency notes put into this. ;-) Great work nonetheless.
Have a look at similar promotion techniques posted in adMad by clicking on the label Guerrilla Marketing.