Things of Middle-earth
A long knife manufactured in Gondolin and taken as war spoil by the creatures of Morgoth in the First Age. It glows with a pale light in the presence of goblins and cuts with unnatural sharpness.
It was found again in III 2941 by Bilbo Baggins, who used it as sword to rescue the Dwarven Company of Thorin Oakenshield from the spiders of Mirkwood, and later named it Sting.
Bilbo gave it to Frodo Baggins in III 3018, to be used in the the Ring quest. It was also wielded by Samwise Gangee against the spider Shelob in the pass of Cirith Ungol.
Then the stone door swung back with one big push, and they all went inside. There were bones on the floor and a nasty smell was in the air; but there was a good deal of food jumbled carelessly on shelves and on the ground, among an untidy litter of plunder, of all sorts from brass buttons to pots full of gold coins standing in a corner. There were lots of clothes, too, hanging on the walls -- too small for trolls, I am afraid they belonged to victims -- and among them were several swords of various makes, shapes, and sizes. Two caught their eyes particularly, because of their beautiful scabbards and jewelled hilts. Gandalf and Thorin each took one of these; and Bilbo took a knife in a leather sheath. It would have made only a tiny pocket-knife for a troll, but it was as good as a short sword for the hobbit.
'These look like good blades,' said the wizard, half drawing them and looking at them curiously. 'They were not made by any troll, nor by any smith among men in these parts and days; but when we can read the runes on them, we shall know more about them.'
The Hobbit, Ch 2, Roast Mutton
There was the usual dim grey light of the [Mirkwood] forest-day about him when he [Bilbo] came to his senses. The spider lay dead beside him, and his sword-blade was stained black. Somehow the killing of the giant spider, all alone by himself in the dark without the help of the wizard [Gandalf] or the dwarves or of anyone else, made a great difference to Mr. Baggins. He felt a different person, and much fiercer and bolder in spite of an empty stomach, as he wiped his sword on the grass and put it back into its sheath.
"I will give you a name," he said to it, "and I shall call you Sting."
The Hobbit, Ch 8, Flies and Spiders
He took from the box a small sword in an old shabby leathern scabbard. Then he drew it, and its polished and well-tended blade glittered suddenly, cold and bright. 'This is Sting,' he said, and thrust it with little effort deep into a wooden beam. 'Take it, if you like. I shan't want it again, I expect.'
The Fellowship of the Ring, Book II, Ch 3, The Ring Goes South
Then Frodo's heart flamed within him, and without thinking what he did, whether it was folly or despair or courage, he took the Phial in his left hand, and with his right hand drew his sword. Sting flashed out, and the sharp elven-blade sparkled in the silver light, but at its edges a blue fire flicked.
The Two Towers, LoTR Book 4, Ch 9, Shelob's Lair
Contributors: Dim Genesis, 06.06.03
Quotes added 6.15.03, 12.5.04 Lyllyn; Naming added: Elena Tiriel 5.26.04