> * Take a microcontroller that just doesn't have a facility for reading
> the code memory out of it. No facility. At all. Fullstop.

As others have already told you this does not exist. Intel did go through a 
loop at one stage with ROM version of their 8041 and 8048 micros, where they 
would factory test the bare chip, and then not bond the wire that allowed 
the ROM to be read. But that was easily got around.

These days there are very sophisticated techniques for finding out what goes 
on inside the chip - and without dismantling the chip. By measuring the 
small amount of EMC energy given off during operation it is possible to 
determine what parts of the chip are operating, and with a little knowledge 
(that may require opening one up to determine the actual chip type) it is 
possible to determine the program execution loops and operations of running 
code. These sorts of techniques are well known in military circles (look for 
the US Forces 'Tempest' range of equipment to see what measures are taken to 
stop this). 

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