Urotropin, also called Hexamethylentetramin is one of these substances. It is a white, cristal-like powder with a strong fishy smell from amines. The structural formula of urotropin is considered beautiful among chemists.
In medicine it is used for bacterial infections of the urinary tract (hence the name). Interestingly, urotropin does not possess any antiseptic function. Only in acidic medium formaldehyde is released, which has a disinfecting effect.