Horny Little Devil
Both the stag and the bull play strong rolls in
pre-Celtic and Celtic imagery, so it is natural to
see a major male god depicted with horns.
Interestingly enough sites in Hertfordshire,
Welwyn and Barton are among the ones who
have located artifacts which depict horned
animals with knobs or balls at the tips of them.  
The horns are integrated even in typically
horn-less animals;  for example a snake with
ram's horns usually accompanies the stag god
One of the names for this god is Cernunnos.
Animals and their Religious Attributes
horned god:  virility, wealth, prosperity
ram-headed serpent:  war god, healing
ram: war, warriors, fertility
raven:  prophecy, war, fertility
generic birds:  mother goddesses, messengers
horse:  female fertility, maternity
swan:  sun gods
aquatic birds:  sacred hot springs and other
religious water sites
goose:  ill-omen
eagle:  sun gods, kingship
crane:  transformed humans; mean women
cow:  magic
boar:  warfare, magic
dog, wolf:  companion
bear:  protection, admirable traits
hare:  hunting, success,
fish:  knowledge from the "other side"
Common combinations of animals with
religious significance:
ram-horned snake
triple-horned bull
stag-horned man
Types of wild animals with religious
significance:
bears
boars
cranes
crows
ducks
eagles
geese
hares
ravens
snakes
stags
swans
toads/frogs
Golowan - The Cornish
St John's Feast
Celebrated at
Midsummer, this festival
features some key
pre-Christian characters
including Penglaz, a
fertility horse decorated
in a wreath and ribbons,
a festival of fire, a
serpent dance, a
traditional fair with a
mock Mayor, and
recognition of the sea.  
Penglaz is usually
represented with a horse
skull (as you can see
from the picture on the
left).
Types of domestic animals with religious
significance:
bulls
dogs
horses
Swearing on the Horns

The photo is from Highgate in 1906.  
At one time there were about 20 public
houses (bars) in this part of London
which made strangers hold a pair of
antler horns and swear to basically
have fun.  Although this custom has
largely died out, a pub called The
Wrestlers still performs the ceremony
twice a year.  There are other events
around London which link to
celebrating the Stag-horned god.
The Horn Fair, London

The current one is a revival of the one
which continued until authorities
stopped it in 1876.  Although gaining
popularity, the original had people
frolicking in a frenzy wearing play
antlers. To gain additional perspective
on how far back this tradition went,
there is a place in nearby Greenwich
names Herne Hill and where St Paul's
Cathedral now stands was a temple
dedicated to Diana (Roman Goddess
of the Hunt).
Worship of the Stag Horned God into the
Renaissance

I've got one word for you...Shakespeare

The Legend of Herne

There is an old tale goes that Herne the Hunter,
Sometime a keeper here in Windsor Forest,
Doth all the winter-time, at still midnight,
Walk round about an oak, with great ragg'd horns;
And there he blasts the tree, and takes the cattle,
And makes milch-kine yield blood, and shakes a chain
In a most hideous and dreadful manner.

You have heard of such a spirit, and well you know
The superstitious idle-headed eld
Receiv'd, and did deliver to our age,
This tale of Herne the Hunter for a truth.

"The Merry Wives of Windsor", Act 4, Scene 4, William
Shakespeare

n.b. Herne the Hunter is connected with the stag
imagery/Cernunos AND Green Man imagery
Here is a tribute film to
Cernunnos/Herne the
Hunter I found
interesting - you can see
additional use of the
stag god's imagery:
Cernunnos