The riot shotgun is a 12 gauge shotgun in Syphon Filter: Omega Strain which uses bean bag ammunition.
"This is a modified combat shotgun that fires bean bags instead of standard shot. The bean bags inflict a non-lethal, though extremely painful, shot. Users of this weapon are cautioned against head and neck shots because they will cause severe brain trauma and, in many cases, death to the victim."
This weapon is obtained by earning Mujari's commendation. Argubly it is inferior to high damage shotguns because it only knocks enemies out; but technically shotguns are lethal in close range. This shotgun suffers from further disadvantage because one must be very close to a victim to kill him (it cannot pierce body armour).