Bilbo’s sword in J.R.R. Tolkien’s The Hobbit is named Sting.
Bilbo finds the blade in a troll-hoard alongside two larger Elvish swords, Glamdring and Orcrist. Because the sword is short by the standards of Men and Elves, the Dwarves initially regard it as a dagger. Bilbo names it Sting after using it against giant spiders in Mirkwood.
Sting has a distinctive property: its blade glows blue when Orcs or Goblins are nearby. Bilbo carries it through much of his adventure, and later gives it to Frodo. Frodo uses Sting during the journey to Mordor, including inside Shelob’s lair.
The three blades are often confused because they come from the same troll-hoard. Glamdring belongs to Gandalf, and Orcrist is associated with Thorin Oakenshield. Sting is the smaller blade carried first by Bilbo and later by Frodo.