Re: Are there any practical uses for gamma rays?

Yes.  Many uses.  Radiographing is the same as X-raying, but it doesn't 
require a source of electricity.  Therefore, a source of a gamma ray 
emiting isotope, say, Cobalt-60 can be taken to such sometimes remote 
places as construction sites and oil fields.

In construction, radiographic pictures are taken of welds to check for 
flaws, and the same source can be used for "well logging," a process for 
determining info on all sorts of parameters associated with drilling and 
reservoir management in oil fields.

There are many medical tests that use gamma ray emitting isotopes for 
diagnosis.  Radioactive Iodine is used to diagnose problems with the 
thyroid, and another isotope is used in the analysis of the operation of 
the heart.

Is any of this dangerous?  Yes, but like dynamite and power saws, this 
material and equipment must be handled with respect, but not with fear.  
Experience with it eliminates misgivings.  

And, the benefits of its use far outweigh the risk.