Not mine personally, but I know of people who have a problem with their belly buttons and a nasty odour. No matter how often it is cleaned or how big or small (fat or skinny basically) the surrounding area is it still stinks! Any ideas on why this is? I know of at least 4 cases of hygenic people who unfortunately suffer from this.
the best thing for them to do is wash and dry it thoroughly after a shower as this area often gets overlooked and moisture is a great breeding ground for bacteria