First off, you're using a very relative term - "best". What's best for one application may not be for another. If best in your mind is a .22 that you can shoot cheaply to plink cans with, it's not going to be the best for hunting bear, by a long shot.
Furthermore, that type of gun? There are several. Handguns, shotguns, and rifles all have different applications, and none is ideal in every way for the role common to each.
the best gun from WWII had to be either the trench gun(a shotgun) or the springfield. no questions asked. The most reliable are the lee enfield and the 7$ gun(stengun)
no the m1garand <><><> There is no ONE "Best" gun.
Most veterans and historians think it is the M-1 Grande
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The Ak 47 is the most commonly used weapon today, and is considered the best gun for most assault situations
Ray Gun
The German 88mm
The longshot or longstrike
the most fps in a gun is 500 or more and my best gun is a mp44 because its 517 fps and it hurts and it feels like a bb gun
Most folks use a 12 guage shot gun.
AK-47
Top Gun