When you look at the areas of the world that face life threatening problems, IE: earthquakes, flooding, war, those things that are needed immediately should be something to consider.

A perfect example is the Bird Flu scare, there are companies that are now selling kits with masks, antibacterial waterless hand purifier gels, a pair of surgical gloves, goggles, and water. This is exactly what I mean. It is something that someone figured that as humans we will need in the near future. It is a life threatening flu and people will pay almost anything to insure they stay healthy, and alive.

Telephones are necessary in this day and age!
Groceries, baby diapers, antibiotic creams/ointments, pure water!

Think of the things that require life support if you loose power, can’t get to the store for a week or more, a way to keep warm (heat), a way to remain "clean" when there is no tap water for a shower or bath, a way to cook food?

These are all the things that make the most profitable incomes.
If you don’t need it to stay alive, its not something that will bring in a lot of money when people have to use their money to survive
References :
When I began my own business I wanted to be sure it was something that the human population would always need! Selling things that folks could live without could be in jeopardy should a disaster strike.

http://www.irs.gov/charities/article/0,,id=96136,00.html
References :
tax cpa