A con artist or confidence man was a person who gained another's confidence through trickery, then exploited that trust for his or her own gain. This was a form of fraud.
Martus Mazur was an El-Aurian con artist who used his natural powers to con a variety of people on Deep Space 9 in 2370, including Alsia and Roana. Quark saw past his charms and realized he was a con artist. (DS9: "Rivals")
The Ferengi Arridor and Kol conned the people of a primitive Delta Quadrant planet into thinking that the two Ferengi were the Holy Sages, demigods spoken of in the epic poem Song of the Sages. The crew of the USS Voyager put a stop to this after Commander Chakotay and Lieutenant Tom Paris discovered the exploitation while investigating the possible presence of a wormhole to the Alpha Quadrant, as well as the signature of a replicator from the Alpha Quadrant. (VOY: "False Profits")
Dala, Mobar, and Zar were con artists who in 2376 impersonated Captain Kathryn Janeway, Lieutenant Commander Tuvok, and Commander Chakotay, respectively, in a string of fly-by-night scams. (VOY: "Live Fast and Prosper")