Dungeon Masters, What Is the Most Useless Item You Gave Your Party and They Exploited?

Welcome To AskReddit Is Fun https://www.youtube.com/channel/UCyO5LhbJlmBXqEPSxKascsA?sub_confirmation=1 ▶ Fresh AskReddit Stories: Dungeon masters of reddit, what is the most USELESS item you gave your party that they were still able to exploit?