I Finaly got "Artifact 19" on "Thing thing Arena 3" its preaty sweet, if you do already have it here is a tip: Artifact 19 uses more ammo when you firing it only one person, wait till there a 4 people on screen and then unleash hell.

If you dont have the Artifact then all you have to do is get the 100 kills achevment with evey weapon, no you dont have to get them in one round....that would be tough, anyways good killing! peace!!