I did this in my counselling group only last week. It's a great activity.
Along the same lines, we had to describe each other (positively) as animals, musical instruments and food, giving reasons. We had such things as : A swan, because you're graceful, a drum because you make a noise, but you have important things to say, a fish, because you're laid back and cool, a lion, because you're a leader, and you're brave, a piano, because you have alot of range and you can change a lot, a chimpanzee, because you're fun, a dog, because you're loyal, curry, because you can be fiery, sald, because you're cool, etc. You might want to give them some examples to set them off. It was great fun, and very constructive.