You mean as in the Camelot of the Arthurs legend?
I don't think there is a specific mention of a coat of arms of Camelot or Arthur in the old sagas, but there are many symbols.
Perhaps the most famous is the round table. It was so popular a symbol that some medieval lords ordered for their own round tables to be build. The most famous still existing example is exhibited in Winchester:
It was built in 13th century but the coloring and inscription of names was added in 16th century.
Symbols strongly associated with Arthur (not as much with Camelot as a place) are the swords Caliburn (the sword Arthur pulled from the stone and later broke in battle) and excalibur (the sword he got from the lady of the lake to whom he ordered it to be returned after he was mortally wounded. Excalibur is often depicted in the hand of the lady of the lake at the lake's surface:
Arthur's father Uther Pendragon is sometimes associated with a dragon on his shield, but I don't know if this was ever linked to Arthur. Sometimes Arthur has been attributed with the golden lion on red ground which became the coat of arms of England, but the association is more based on the attempts of later real monarchs to claim their rule as a continuation of Arthur's rather than any mention of such a coat of arms in early arthurian texts.
There are mentions of some coat of arms of specific Arthurian knights. Sir Gawain for example is mentioned in the tale of Sir Gawain and the green knight to have worn a red shild with a pentagram on it (the points of the star standing for the wounds of christ) and Mary painted on the inside of the shild if memory serves me right.
There is
this page on Arthurian heraldic, but I only just found it and cannot really say to what degree coats of arms there are based on any texts or the phantasy of more recent authors or artists.
PS: ^ Without any reference to sources on the above page and it not being from some known institution I think that the coats of arms there are more likely recent interpretations.
