Perfect Pocket Gun
There are a lot of pocket guns out there starting with the North American 22 short and going to small 9s & snub nose revolvers. I carry the Kel-Tec p32 & while it's a perfect size, in an emergency I'd like a higher caliber.
The gun I'd like to see is a light wight, de horned 4 round 38 snub nose from a name manufacturer. If I were designing it, I'd steal the idea of a flat rather then a round cylinder which would reduce size. Wherever possible, I'd use titanium or aluminum or other light weight metal that could bring it in at 10 ounces or less.
Such a gun would vanish in a front pocket, but still be instantly available with 4 shots with pretty good stopping power. You could additionally still carry a normal sized gun in the small of the back, if the 4 rounds don't cut it.
Lastly making a revolver that isn't picky about ammo and goes bang every time the trigger is pulled is achievable. I also see a real market for this type of gun, particularly in urban areas.
The icing on the cake for the manufacturer is they could use most of the same machines that they use to make their regular snubs. It wouldn't entail reinventing the wheel, pretty much just tweaking the wheel.