Guns
Guns should be specialised per category, i.e. all SMGs should feel like SMGs even if their stats are different.
Guns are going to be designed around range, with the exception being launchers (typically specialising at area damage) and lasers (specialising at going through glass). This means the MaxAngle for every gun in a class should be the same, with every other lever being able to be tweaked. The reason behind this is to make each class clear at what it does and avoid a gun overstepping its bounds and overshadowing another category.
Rifles:
Should be the default gun, being accurate enough to shoot a mob anywhere on screen (that is, its max accuracy is never wider than their hitbox). From here:
Shotguns:
Very short range, being only able to hit all of their pellets up to ~3 tiles away. The exception to this are slugs which should provide the accuracy of a rifle but not the damage, only being used as a last resort.