1. You can get bitten by mosquito's, causing West Nile ( http://en.wikipedia.org/wiki/West_Nile_virus ) or Malaria ( http://en.wikipedia.org/wiki/Malaria )
2. People are retarded or something and let their big ass dogs walk without leashes, which can lead to you being attacked and getting Rabies ( http://en.wikipedia.org/wiki/Rabies_virus ), and that is assuming you are lucky enough you don't get mauled to death by the dog.
3. Poppy seed sized bugs, called Ticks, can give you Lyme Disease, which can cause "Many disabling symptoms can occur, including permanent paraplegia in the most extreme cases" ( http://en.wikipedia.org/wiki/Lyme_disease )
4. Bears can attack and kill you
5. Getting hit by a car
6. The sun releases radiation, which can give you skin cancer ( http://en.wikipedia.org/wiki/Skin_cancer ), Heat illness ( http://en.wikipedia.org/wiki/Heat_stroke ), and burns.