I had limited experience in the past with clone or copy of those guns, the PP-90, while it makes it invisible to most people, and will be able to go with you if its legal to carry anywhere you'd want to. Color it in pink and add USB cable and you will never get a second look. But it is bulky, and the ergonomics of the PP-90 are horrible. I would be ideal for clandestine operations, but useless in any civilian application, and in order to take advantage of the design you'd have to carry it in your hands, and not on the holster, or a sling.
The cool factor is however there through the James Bond gadgetry.
The most interesting concept I've seen was suit case, with small machine gun in it. the way it worked was you hold the handle on the top, pop the case open. Inside was a short barreled belt fed machine gun. The Suitcase itself was armored. So in theory the gun was supposed to be pulled, it would swing perpendicular to the case, the barrel then would point out of the suitcase, and you'd end up with a with a shield and machine gun.
It was a cool theory, but the damn thing was so heavy and unreliable, that it defeated the entire purpose of the weapon. Still a cool concept.
