When writing The Troubleshooter, I had to come up with the types of firearms that would exist in the retro-futuristic world of New Haven. Mick Trubble carries two main guns. His first choice is the Mean Ol' Broad, a heavy duty piece that fires explosive tipped slugs. I had a mental picture in mind when I wrote it: the pistol that Harrison Ford packed in the classic sci fi film Blade Runner. Recently I came a across a site called Johnson Arms who makes props and replicas, including this beauty used with permission by Mr. Johnson:
I really love the look of this weapon. I'm not a firearms expert so I can't tell you how realistic its design is, but it definitely has that retro-futuristic feel that's prevalent in my story. So while this wouldn't be exactly what the Mean Ol' Broad looks like, it's close enough.
Mick's backup weapon The Replacement Killer is a gyro powered handgun that fires miniature rockets instead of bullets. A thing of the future? Nope, of the past. Ironically enough, this weapon is entirely grounded in reality. There was an entire family of Gyrojet firearms manufactured in the '60s as experimental weapons. There's a pretty fascinating article about the history in Wikipedia.
So I got a chance to blend in visions of the past and the future with some of the conceived weapons in The Troubleshooter. There are others: mechanized versions of shotguns, tommy guns, and then the bioguns, which are the most futuristic. Basically they are handguns powered by the energy of the user via cables that insert into the forearm. I'd love to show an example of what those look like but I don't have anything available right now. I'm not all that talented with drawing anything mechanical, so I'll have to collaborate with someone on that. Hopefully I can create a part two of this and show some more examples.