I've also used that black sharpie to color in the scuff marks on black shoes. Sharpies are handy little things!!
About a hundred years ago when I was on active duty, my office mate forgot his black socks and we had a reception at the commanders quarters after work. Being the resourceful young officer he was, he took out a black sharpie and proceeded to color his ankles black. After he was finished, I reached into my top desk drawer and took out the extra black socks I always kept there and tossed them to him.