The term good luck charm referred to a person or item whose presence was believed to bring luck to a crew or an individual.
Shortly after meeting Harry Kim in 2371, Tom Paris warned him that he was not exactly a good luck charm, advising Kim to stay away from him. (VOY: "Caretaker")
Alexander Rozhenko was considered a good luck charm by the crew of the IKS Rotarran, who he claimed felt more safe the more mistakes he made. (DS9: "You Are Cordially Invited")