Katori-Senkou, sometimes referred to as Mosquito Coils, are in my opinion one unique smell that has stuck with me since I first came to Japan.
These coils are like incense, and you light one end to have it burn around and around until it becomes ash. They are very cheap, and provide very good repellent from mosquitoes, even camping near water on the most humid summer night.
No need to rub alcohol based repellent on your skin anymore, the light smoke from the coils takes care of any mosquitoes in the area and makes your outdoor adventure bearable.
The smell is of light burning wood, and in my opinion serves just as well as a stick of incense. Some people don't really like the smell, but I find it pleasant, and it always reminds me of my first days in Japan.