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 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")