Gawain
Gawain - or Wayne as he prefers to be known - is a magical talking sword who appears in The Watch. He was crafted from octiron by "the sourcerer" for King Veltric, along with the Crown, and designed to be wielded only by the true king.
Wayne's voice can only be heard by "true lovers", though he says that "anyone with a bit of love in them" can do so. His major power is that when combined with the Crown and a source of the King's blood, he is able to control a Noble Dragon after it has been summoned.
Gawain appears in the episodes "Twilight Canyons", "Not on My Watch", "The Dark in the Dark" and "Better to Light a Candle". He is played by Matt Berry.
Annotations
Gawain/Wayne may have been partly inspired by Kring, the talking sword who appears in The Colour of Magic.