Carry a small hotel-size soap bar to some areas of the world where the soap may be quite harsh. Sweater or light jacket. Comes in handy where air-conditioners are turned very low. A simple solution for very cold areas. They take very little room but provide much warmth.
Some countries use tissue with the texture of newspaper.
Remove center core and press flat. Take very soft tissue and use in place of Kleenex. Tooth brush cap. A cap for over the brush takes much less room than conventional tooth brush holder. Don't forget maps, travel books.