Drawing Chinese Whispers:
The greatest sketching game of all time! In a group, each person has 3 minutes to draw anything that they like; They then briefly show this to the person sitting directly next to them who has to draw a copy from memory before showing their interpretation to the person sitting next to them. Each copy is made from the last copy (as in Chinese Whispers) until it has passed through the entire group.
The way the drawing gradually changes and evolves is fascinating, and putting the original next to the final version shows how one artist taking influence from another over time creates something entirely new.