the remengtion 870 express mag 12 gauge
The best place to get shot by a gun is the Legs, Arms, or Butt No just the arms.
There is no "best gun", even tough the shotgun does have a one shot kill ability.
Single shot 12 gauge.
the best gun is the m1 garand 1 shot kill
Most folks use a 12 guage shot gun.
Head or Heart shot
Single shot bolt action .22 rifle.
best left to a gunsmith
Rifled slugs are actually INTENDED for smoothbore shotguns. Sabot slugs are intended for rifled shotguns. Performance will vary from gun to gun, but Modified choke seems to give the best accuracy with rifled slugs for many shotguns.
No
Slugs! If its rifled it is a deer hunting barrel.
Best to ask a gunsmith for help