The sword Bilbo found in the trolls’ hoard in J.R.R. Tolkien’s The Hobbit was called Sting.
Bilbo discovered Sting alongside two larger elven blades after Thorin’s company escaped from the trolls. Although the weapon was small enough for a hobbit to use, it was an ancient blade made in Gondolin during the First Age.
Sting had a special property: its blade glowed blue when Orcs were nearby. Bilbo used it during his adventures, including his encounter with the giant spiders of Mirkwood, and later gave it to Frodo Baggins.
The sword is often confused with Glamdring and Orcrist, the two larger blades found in the same hoard. Gandalf took Glamdring, while Thorin carried Orcrist. Narsil is a separate sword from the history of Men and was later reforged as Andúril.