Think about it. The people in the safety equipment production business would make a killing. They'd have to produce more helmets and kneepads quicker than they could keep up with.
As for the actual state of the world, I'd say the people in Africa are the first to go. Look at how many dangerous animals and reptiles roam that continent. Retarded Africans would get stung, bit, eaten, and overall dismantled because they couldn't resist trying to pet the lion, or they had to try and jump rope with that giant cobra.
People living right by a body of water would drown. They'd see their reflection and try and chase after it. I'm guessing most of the mentally challenged can't swim unless they had some sort of water wings or floatation devices with them.
Overall, death would be a common theme.
