Although, not an OFFICIAL guild, they are a group called "Caste". It's lead by a Weavile (
[CLASSIFIED]) who acts as the Guild's top Assassin, Bounty Hunters, etcetera. They're called "Caste" because they're outcasts of the Guild system. They allow many Pokemon as long as they can fit into their rankings and prove to be one of the best of fighters.
Known Members:
-Mochi (Sneasel; Assassin Trainee)
-Soro (Zoroark; Fullfledged Assassin and Bounty Hunter)