I still think the paper made crossbow type weapon they make on mythbusters is pretty amazing. And if you go to San Quentin definately go to the musuem and see the gun one inmate created. Pretty amazing stuff.

I remeber in Gibson's bridge trilogy all the bike couriers had switched paper-cored bikes. I always wanted to see how that would work, it certainly sounded good. So did the locks that unlocked using your wrist as ID.