What is the name(s) of King Arthor's horse(s).  More specifically, the
name of his favorite horse, if he had a favorite.

Hi dn5cents,

I've found two names of horses owned by King Arthur.  They are both
mentioned in the Tale of Culhwch ac Olwen, which is one of the stories
that make up the Mabinogion, a collection of ancient Welsh tales.

It seems he had a mare called Llamrei (or Llamrai) and another horse
called Hengroen.  (Apparently the name Hengroen means “old skin”, so
Arthur either can’t have been that impressed with this horse or else
was very fond of it and liked to tease it!)

I found the information by searching Google for “Arthur’s horse”,
which initially led me to a web site with a mention of Arthur having a
horse called Llamrai, but with no further details of  sources
http://www.kingarthursknights.com/theland/llynbarfog.asp

I found confirmation in a piece about Arthur’s animals at
http://www.geocities.com/dagonet_uk/weaponry.html  on a web site
called “Arthurian Byways” The name is given as Llamrei there. It also
says that Arthur’s dog was called Cavall or Cafal, which means
“horse”!
“Arthur also had a mare called Llamrei that is mentioned in Culhwch
and Olwen. During the pursiut and killing of the 'Chief Boar
Ysgithryrwyn' it is ridden by Caw of Scotland. Llamrei must also have
been able to bear great loads, for she carried four of Arthur's
wounded companions after they had been thoroughly drubbed by the Black
Hag in her cave.”

I have also found a reference saying that apart from Llamrei, the
Culhwch and Olwen story also mentions that Arthur had another horse
called Hengroen http://camelot.celtic-twilight.com/infopedia/a/arthur_possessions.htm
 This is from an “infopedia” about Arthur.

You can find the text of Culhwch and Olwen at
http://www.sunysb.edu/eurolangs/mvl141/culhwch1.htm  put up by
Professor Thomas Keith of Stony Brook University, NY

I have found that the name Llamrai is listed as appearing in the  Book
of Taliesin, another Celtic source for the stories, as well as in the
story of Culhwch ac Olwen
http://www.cus.cam.ac.uk/~jbc1000/Names.html   Page by John Coe of
Cambridge University, UK

Thank you for this fascinating chase through Arhurian legend!

Thanks, this was great!  I have been looking for over a 2 weeks now,
and this is the best answer to date.

PS Hengroen (Old-Skin) is also mentioned on the names list by John Coe
as appearing in Culhwch ac Olwen