The Mechanical Engineering Club's first project was simple electrical board game. I challenged my students to create a game that lights up a bulb when a match is made between two items in the game (for example, an organ in the human body and its name). To accomplish this, each student had to both research the topic he'd chosen for his game, and figure out the necessary mechanics. As they worked, I discovered that my students were motivated to learn more engineering terms than were required -- current and voltage, electrons and electrical loads.
The military was excited about these for many more reasons though: smart mines can hop and sense, and therefore the government could argue they're not land mines, they're smart robots. That means they aren't subject to the international anti-personnel landmine treaties. And since they can move, they're much harder to find and disarm. Great for war. Not so great for cleaning up after war.