The WalMart key pictured in RBruce's photo above is almost pictured to scale. The picture could be printed, the key cut out of the picture, and a duplicate made in short order. Very risky. Medeco locks are probably as high security as you can buy. I know the government uses them a lot. Some of their keys cannot be duplicated on an ordinary key cutter.
Keypad locks are getting to be more common but I don't know how secure they are. I have always thought you could pry the keypad off the wall and short out the wires to open the lock but I don't know that it would be that easy. At any rate, if I was going to picture a key in my EDC, I would find a key that fit nothing and use it in the photo. You can't be too careful. Reporting a burglay with several hundred dollars loss and no forced entry causes you to be suspect in the eyes of the insurance company and/or the police investigator.

Just my two cents worth. <img src="/images/graemlins/smile.gif" alt="" />