Weaponsmith

Kill at least one enemy with every weapon in the game - pistols, revolver, shotguns, the Bastard SMG, rifles, the pneumatic guns (Tikhar, Helsing, Volt Driver), the heavy shotgun, flamethrower, knife, throwing knives and grenades. Keep a checklist and make a point of blooding each weapon at least once as you find it; buy any you don't naturally pick up from weapon shops, and mop up the rest on chapter replays.