I was wandering around Wikipedia last night (one of my favorite activities!) and I stumbled across the article on Celtic mythology. I have to admit, it is quite entertaining. Here are some of my favorite little snippets (forgive me if they're wrong, I'm just pulling them from Wikipedia).

-Y Ddraig Goch (the red dragon of wales) once fought with an invading white dragon. His pained shrieks cause women to miscarry and animals and plants to become barren.

-Cúchulainn (the hero of Ulster) was almost undefeatable in battle due to his spear named the Gae Bulga (which sang for the blood of its enemies) and his warrior frenzy. When the "Warp-Spasm" overtook him: it seemed each hair was hammered into his head, so sharply they shot upright. You would swear a fire-speck tipped each hair. He squeezed one eye narrower than the eye of a needle; he opened the other wider than the mouth of a goblet. He bared his jaws to the ear; he peeled back his lips to the eye-teeth till his gullet showed. The hero-halo rose up from the crown of his head.
This frenzy caused him to turn about in his skin; his sinews bulged with knots the size of a baby's head; a poisonous black mist rose above his head; and he snapped his jaw shut with enough force to kill a lion, showering sparks. In this fearsome state he could not tell friend from foe, killing in front and behind alike.

-The Morrígan (the phantom queen of death) keeps a tryst with the Dagda before the battle against the Fomorians. When he meets her she is washing herself, standing with one foot on either side of the river Unius. After they have sex, the Morrígan promises to summon the magicians of Ireland to cast spells on behalf of the Tuatha Dé, and to destroy Indech, the Fomorian king, taking from him "the blood of his heart and the kidneys of his valour".