This toy model is based on a patent design for a real weapon from 1915. I've made changes to it, including shortening the blade and having the barrel of the gun emerge from it. I had some trouble getting the cylinder to look right, so wound up going kind of heavy on the subdivision modifier. Lastly, I tried to make it look as if it were made from the same green plastic as the toy army men of the 1950's and 60's.
It looks a lot like the Gunblade from Final Fantasy 7. It also had a revolver and trigger on it's handle.