I was just listening to Christopher McQuarrie talk about how he wrote "Usual Suspects." Apparently he had the end 1st when he presented it to Brian Singer. When an opportunity came about with Japanese financiers McQuarrie wrote the beginning and then filled the middle with various ideas that came from his experiences working for a private security firm, at times as a body guard for diamond brokers. He figured since he knew how security operated that he'd be able to steal from them. Later he replaced the McGuffin with a person instead of money, the person that could identify Kaiser Sozei. Incidentally a lot of the names in the film were from people that he had worked with in the past.