Liam

From Memory Alpha, the free Star Trek reference

Liam was an inhabitant of the holographic 19th century Irish village Fair Haven.

Liam had been undefeated in arm wrestling for three years, when Harry Kim wrestled him. Seamus bet three bob on Liam, while the Doctor initially bet five shillings on Liam but withdrew his bet and placed two shillings on Harry when Tom Paris reproached him. Captain Janeway also expressed her confidence in Harry to Michael Sullivan, the bartender. Despite appearing to lose early in the match, Harry defeated Liam, leaving the Doctor elated. (VOY: "Fair Haven")

According to Michael Sullivan, Harry Kim was the only one in four counties, who had defeated Liam in arm wrestling, so Liam sought a rematch. (VOY: "Spirit Folk")

Liam was played by an unknown actor.