May I suggest pop singers and reality show participants? And please YouTube any experiments for posterity.

Regardless of what can cut through what (nobody's mentioned light yet), the problem with the N900 is that it has, for better and for worse, a resistive screen. One of the "for worse" parts of resistive screens is that they have to be able to deflect in order to measure the resistance. Since it is very costly to produce a screen that is both flexible and highly scratch resistant, resistive screens tend to scratch more easily that capacitive screens which can use glass as the top layer. I would not try the following with the N900::

http://phandroid.com/2009/11/11/moto...with-car-keys/