Hall of Infinite Doors

You wake up in your dilapidated shack. Business has not been good lately and people do not seem to have any use for a large animal exterimator. You were planning on throwing in the towel when you get a call from professor Oak. He asks if you could run down to his lab immediately. You head down and he has layed out on a table three weapons. He then proceeds to tell you about a new infestation of some sort of vermin called "pokemon" and states that he will pay you well to eliminate them. He is offering you three highly adaptive weapons to aid you in your quest, and each one will evolve and its technology will upgrade as you kill more of these creatures. Which shall you pick?