Remember to keep left when driving in the UK or Ireland! An american tourist in Scotland forgot about it and did not get the holiday he was looking for (I presume). This is also one of the reasons it is usually a good idea to not rent a car at the airport and drive away, when you are tired and jet lagged it is easier to make mistakes like this.
While this ended relatively well, with everyone involved being able to walk away from it. A similar accident last year resulted in one death, and created a bit of a diplomatic incident. So please, be careful on the roads!