During August, 2010, this picture of VW’s headquarters appeared in Google Street View. Fiat actually was following a Google car and then parked, at the right moment, in front of VW for the shot.
In Santa Monica, CA, Audi and BMW got into a billboard war. Displaying its A4, Audi first said, “Your move, BMW.” Soon after, BMW responded with its M3 and “Checkmate.”
Then, the following photoshop responses were added online.
Sources and resources: To investigate the auto industry further, this Booz.com analysis is full of details. For more great ads, BusinessInsider has a fun article and here, quora asked for people to submit the best ads.