Sawed-Off Shotgun

With only two shots between a rather lengthy reload, a gun really needs to make its mark to be worthwhile. And make its mark it does- on anyone within about 35° of where you're pointing! Of course this much spread makes the gun pretty much useless in any medium to long range situations, but up close it is a deadly sight to behold. And to make matters worse (for those on the other end that is), getting this bad boy up to the Hitman level allows you to use two at once, which subsequently allows for a rather rapid- and devastating- burst of four shells between reloads. It's also worth mentioning that the gun's small size means it's possible to run and gun with it like a pistol.