Tooting Handshake
A friendly greeting, given by motorists to passers by. It is given in the form of dangling a flaccid penis from a car window, and swerving close to a pedestian so that it slaps them in the face.

Popularised in the Tooting area of London, it is now something of a local tradition.

Best carried out while the car is moving, in case a quick getaway is needed.
"That jogger looks like she needs some encouragement, wind down the window and I'll give her a Tooting Handshake as we go past"