Getting ripped off is no joke when it happens to you. In some countries it is very easy to get ripped off, especially if it is obvious you are a western tourist. Be smart and pay half the price they give you. Some people, whether taxi drivers or bellboys, will be confrontational and at times aggressive, do your best to asses the situation. Don't go blindly into a country without understanding how much it would cost you for common services and goods.
Beggars. When I was in Egypt this summer, I got ambushed by child beggars. It was by far the scariest experience of the trip. I was getting into the car when this young Egyptian girl approached me pleading in Arabic to give her money. When I kindly said I didn't have change on me, she proceeded to grab my hand to kiss it when I quickly jerked it away. I jumped into the car and shut the door, but she started to bang on the windows. I finally found some change and gave it to her so that we could get the car out of the parking lot. Spare yourself the anxiety and try to avoid places populated with beggars. Some don't show any mercy.
Transportation. Depending on what country you are traveling to, transportation can be insane -- in every meaning of the word. Don't walk into the street without being sure cars will stop. Prepare yourself for crazy driving in most places in the Middle East and North Africa.