Vinegar is a wonderful all-natural cleaner. However there are some surfaces that should not be cleaned with vinegar.
Granite and marble - Vinegar contains acetic acid, which makes it a wonderful cleaner for many surfaces. However the acid is too strong for natural stone surfaces like granite and marble and will actually etch the surface. Dish detergent and water is a gentle but effective cleaner for granite and marble.
Egg stains - Egg stains should not be cleaned with vinegar. The acid in vinegar will cause the egg to coagulate and make it more difficult to remove.
Hardwood floors - Again, the acid in vinegar is too harsh for natural wood surfaces. Go with a cleaner that is specifically designed for hardwood.
Iron and aluminum - Vinegar works well as a cleaner for tough metals like stainless steel. However, it shouldn't be used to clean softer metals like iron and aluminum.