I had a driver pull in beside me at a traffic light (we weren't even moving!) and use the self-gratification artist sign.
So sent the video to the Company and complained about inappropriate sexual behavior by their driver. Also asked for a copy of their Equality and Diversity policy as I was an equal rights campaigner for Gay rights and wished to make a formal complaint about sexual harrassment.
Got a wonderful grovelling reply!
Haha love it! Nice one.