We see this trope in comics and manga, and also in cyberpunk fiction, where characters have weapons integrated onto prosthetics, like arm cannons. It can sometimes even be a bit absurd, where guns are integrated onto people's heads, legs, chest, etc.
What were the earliest examples of this in fiction? I'm only looking for prosthetics integrating guns, as many have pointed out that variants like integrated swords or hooks have been around for a long time.
Assuming newspaper comics fit your "speculative fiction" moniker, and assuming a flamethrower is close enough to a gun, Dick Tracy had Dr. Plain as a villain with a prosthetic arm containing a flamethrower in 1950 and 1951.
Dr. Keenan Plain
- One-armed surgeon who murdered many to inherit wealth; ingenious murder weapon
- Flame thrower/prothesis — caused own death
The earliest I can find is Limbo by Bernard Wolfe (1952). A review by The Nihilist Void explains the nature of the "arms" race:
Little do the citizens of either country realize, however, that secretly both governments [the US and the Soviet Union] have been developing weaponized “arms” just in case another conflict between nations erupts. Among their arsenals are flame-thrower arms, rifle arms, and helicopter arms, all of which can be mounted on the stumps of amputees, making them into super-cybernetic warriors; the very opposite of pacifists. Despite the removal of limbs, it appears, the aggressive death drive remains just as strong as ever and human nature is unchanged despite Immob philosophy.
I'll propose Roger Zelazny's Isle of the Dead (1969), in which the narrator Francis Sandow has a laser implanted inside his finger.
He puts it in:
I anesthetized and cut open the middle finger of my left hand, implanted a laser crystal and some piezoelectric webbing, closed the incision and kept the hand in a healant unit for four hours. There was no scar. It would sting like hell and cost me some skin if I used it, but if I were to extend that finger, clench the others and turn my palm upward, the beam it emitted would cut through a two-foot slab of granite.
And in an example of the "Chekhov's laser finger" trope, he uses it:
I raised my left hand, supported it with my right and performed the necessary gesture. I screamed as my fingertip flared and his head fell from his shoulders, bounced once and rolled past me - those eyes still open and staring - and followed my wife and my best friend into the chasm below.
