If you own a bicycle then you really need to have a look at this page. The claim is that 'Kryptonite' style U-Locks (or D locks) can be opened easily with a bic style point pen. There is video.
The flaw is with the locks with the circular style keys. Essentially you find a pen with the right diameter, remove the cap so you have a tube, jam it into the lock and wiggle mightily.
There is a smutty joke in there, I'm sure of it.