"Who am I?" is a great party game for when the party starts to die down, or if your guests don't know each other that well.
It will get everyone talking to each other, mingling and having fun. It's also pretty simple to organize and you only need a few sticky notes and a pen.
Write down names of famous people on sticky notes and stick one to the forehead of each of your guests. Make sure they don't see what is written on their sticky note! And also try to remove any reflecting surfaces in the party area(stuff like mirrors).