Smith and Wesson Model 29

The Smith & Wesson Model 29, also known as the M29 was a six-shot double-action combat revolver, and reputed to be the most powerful shotgun in the world.

History
It was developed on 1955 by S&W for an N-frame revolver and produced around 1957. It was largely kept in the territory of gun enthusiasts, and used as a hunting gun, although it gained popularity in 1971 after the release of Dirty Harry.

Behind the scenes
The M29 has yet to make an actual appearance either as a usable weapon or overall, although it received a brief mention in an optional radio conversation with Para-Medic in Metal Gear Solid: Portable Ops, should she be recruited. In the conversation, she mentioned witnessing a detective use the gun to Big Boss in San Francisco, with Big Boss expressing confusion as it was meant for hunting, and not for detective work, especially as the recoil would have been enough to kill the suspect instantly, alongside the rapport and recoil making its use impractical before Para-Medic admitted that she had seen it in a movie.