Drive up to an intersection, and start honking your horn. Other vehicles will join in and honk as well. If you honk your horn near a police car, they will run their siren to honk with you.

While stopped in a vehicle in a large traffic jam, tap out the rhythm of the musical phrase "Shave and a haircut" with your horn. Another car in the traffic jam or pedestrian will answer it with the standard two beep "two bits" response.