You might not remember this, but Hollywood once tried to convince us that Sylvester Stallone belonged in romantic comedies. They almost pulled it off, too, and that's how you know they're the best masters of disguise in the world. A good movie prop master can create the most realistic device from any old cheap piece of shit laying around. For example ...
5Sci-Fi Guns Are Just NERF Guns Painted Black
Today there's a whole scene of NERF modders who paint and age toy guns to look so realistic that they're forced to play NERF wars in the dark so the neighbors won't call the cops.
Nerf or Nothing Brazil
Or the National Guard.
In fact, the toy guns look so good that they're popping up in movies like 2009's Hunter Prey. The gun below is actually a $30 NERF N-Strike Recon CS-6 Blaster.