In addition to Fingolfin's sword (in Tolkein), this is the single best weapon (arguably) in Vanilla Angband, and one of the best in many of the Angband variants. Among other things, it gives a +10 to speed, more than any other artifact.
At least in Vanilla, Ringil is easily spotted because its dice damage is different than that of a normal longsword. This leads players, especially those playing it with preserve mode off, to chase it, often to the extent of risking the life of their character.
Oh, in reply to a /msg I got - this is NOT a game with stats. This is Angband, a roguelike game somewhat like nethack.