Bananas.

You don’t need to eat bananas for the potassium! (Although it is present in bananas, potassium is the predominant nutrient among most all fruits and vegetables.)
Bananas are high in sugar, so they should not be eaten if you have blood sugar problems.
Don’t eat bananas on an empty stomach; combining them with a bit of protein will help to normalize the insulin response caused by the sugar in the banana.
Green-tipped bananas are better for your health than over-ripe bananas.
On a side note: Because bananas are so popular, rainforests are often destroyed to make way for banana plantations.