In my third year class, we were talking about the five senses. To best use the sense of touch, students had to put their hand into (Kwandong)Brian's Big Box of Mystery. Inside were a wooden block, an open Swiss Army Knife*, some plastic toys a cassette tape, a bolt with wingnuts on it, a few chocolates, a chess piece and a baduk piece.
The box wasn't really that deep - I taped in a divider about halfway. The opening was covered in three layers of paper cut into ribbon but also with "Abandon all hope, ye who enter here".
We also performed a sort of Buddhist food meditation that I learned at KOTESOL from Marc Helgeson. It involved using all five senses to study the food before eating it. We looked at the food (a chocolate, which is probably sacriligious), listened to the crinkling of the wrapper, smelled the chocolate (wiped the drool), felt the texture of the chocolate on our tongues, then finally bit down and considered the taste.
It seemed like a excellent start to the class, although the BBB of M would probably be better for a children's class.
The Swiss Army Knife was open to the nail-file, not a sharp blade. Still, when a student found it, you could tell by the look on his/her face.