I had originally thought this up as a good solution to the Star Trek problem wherein an alien steals your phaser, but it would work in current-day situations to a certain extent, with certain modifications.
Most weapons are similar in that they have a handle at the opposite end of a barrel-like
object. Since this is a fairly logical layout for a weapon, one might imagine that even alien cultures would figure out how to employ it if they are built with limbs like ours/saw others holding/operating the weapon.
This is why mork is able to steal your phaser and escape the cargohold successfully.
The idea is a weapon which fires "backwards" unless actuated in a convenient but non-automatic way. Convenient means that in the heat of the moment, you will easily know how to properly discharge your weapon. perhaps some microswitches tailored to the lengths of your fingers. Many options available, chosen by the purchaser of the weapon.(fingerprint reading is unreliable, DNA is judge-dredd fantasy)
When your enemy steals your gun, if they do not hold it in a certain way*, the [projectile/energy pulse] is fired out of a concealed rear-facing door, killing your foe***.
For projectile weapons (guns), there would have to be a separate hammer, chamber, and even a pre-loaded backwards bullet, all hidden behind some break-away door that doesn't look like it is hiding a barrel.
Alternately, an unintuitive safety-lock which, if not operated, applies high voltage across the grip (the safety will keep the muscular impulse of contraction from firing the weapon properly).
If this is an electrically based space-weapon as seen in sci-fi, it is that much easier to do.
You may consider this to be half-baked by the invention wherein a wristwatch acts as a proximity-safety device in some implementations. Those won't disable your foe!
*- the wristwatch idea can also be used as the unique firing method, however, many people use their weapons as home-safety devices and might not think to put on a watch if an intruder intruded at 4am.
--i have never owned a gun. This originally started out as a 1-line star-trek joke idea, but then i started imagining all the comments about how it was a "magic" idea, so i turned it into a real thing, then i had to account for comments on the real thing, and really, it all got out of control, didn't it?
***-Alternately, one of those flags that say "blam!" - this would diffuse the situation, laughs for all!
As always, if you have children, lock up your fsking guns.
Humans have trouble with this alien six-shooter
[ldischler, Jan 26 2008]