Place three cans (soda cans are easier to work with but other cans will work) on the table along with some paper, tape, and string. Tell your students to make something, anything.
They may use scissors or other cutting utensils during construction IF SUPERVISED (this is pretty dangerous and it is easy to cut yourself). Scissors may not be a part of the solution.
When they are done, but not before, show them this and this and this!
These are really cool!