Jee Young Choi's slotted toothbrush design provides a handy way to squeeze that last drop of paste out of the tube. The hollow sidewalls of the shaft allow inner surface of the slot to compress inwards to accommodate tubes of varying thicknesses.
The concept arose out of Choi's desire to extend the life of a toothbrush; she noticed that her mother often saved old ones for cleaning, as many of us do, and the slot is meant to give it a second function as a squeezer-outer of other tube-based goods (i.e. oil paints, caulking and what have you).
Choi's full concept boards are up on Coroflot.