Each upgraded weapon replaces the last in the category, except the Walloper, Katana and Assault rifle.
Only used for silent kills
1st weapon slot
Advanced Axe (replaces previously equipped axe)
Lever Axe required to open certain doors (replaces previously equipped axe)
2nd weapon slot
Silenced Pistol (replaces pistol)
The Walloper (uses pistol ammo)
3rd weapon slot
Assault Rifle found in the underground tunnels in the lap of a dead guard, (uses shotgun ammo).