On a similar theme, going slowly along a road because, due to the heavy traffic, you know that if you go any quicker you'll just slam into the back of the queue for the next roundabout. This leaves a gap of over 100m between you and the car in front. Some impatient imbecile behind beeps their horn and does a slightly dodgy overtake, making moronic gestures as they pass, and immediately has to slow down as they slam into the back of he queue. You carry on like nothing happened, and arrive at the back of the queue when there are only one or to cars in front. Including the one which overtook. You can then be smug that their aggressive driving style didn't achieve anything, other than slightly increase the amount of fuel they used for their journey. Even better if you give them a friendly wave...