-From a historical perspective, they have a lot of history attached to them. Wars, mainly, but other things too, like crime, espionage, and even general culture in some cases. it can be interesting to read up on the design philosophies that makes a gun designed the way it is as well as the doctrines that give said guns a reason to exist, in the case of military rifles atleast. You could endlessly read up on the who's and why's criminals, policemen, armed citizens & others tend to use the guns they use if you wanted to.
-From a design perspective there is a ton of R&D put into a gun. on all but the most jerry-rigged guns out there, there is effort that is put into even the smallest of details that you'd normally miss. I honestly dont know how to put it into words; I had no idea the sheer amount of thought and reasoning put into the design of guns until I did some actual research into them. it is mind-boggling and pretty impressive, all things considered.
-From a competitive perspective there is a level of skill & nuance needed to use a firearm proficiently; it can take a lot of practice & knowledge to become good with one, and naturally there are endless conversations about "how" one should shoot a gun, as you might expect.
There are plenty of things about firearms that one could find interesting, and as such there are endless amounts of things that a retard could ramble on about and get into irrationally heated debates over. Thats why we're here.