Over the years, in helping many seniors attack their application essays, I have always been surprised at how many of them are stumped for ideas, especially when faced with the "Any topic" prompt. Essay ideas are everywhere; we just don't see them.
Since I have been working with high school seniors for so many years, I go about my daily life with a "That would make a great essay topic!" mindset. For example, I tend to be an acute observer of human nature and its behavioral consequences. Shopping can be a wonderful source of essay-idea inspiration. One day while I was in the grocery store, I noticed a man placing his selected items in his cart in a very particular manner: small items went in the child seat section up by the cart's handle. Medium-sized items went in the back of the lower section. Larger items, such as big boxes of laundry detergent and bags of dog food, went in the front.