In The Hobbit: An Unexpected Journey, Bilbo’s sword is named Sting.
Bilbo Baggins finds Sting in the trolls’ hoard during his journey with Thorin Oakenshield’s company. The blade is one of several ancient Elvish weapons recovered from the hoard, and it later becomes Bilbo’s characteristic sword. In Tolkien’s world, Sting glows blue when Orcs or other creatures associated with them are near.
The sword’s name is a deliberate contrast with its small size. Bilbo is a Hobbit, so a weapon that appears short to a human or Elf can function as a sword for him. The name also foreshadows the weapon’s effectiveness against giant spiders and other enemies.
Glamdring and Orcrist are the other famous swords found in the same troll hoard. Andúril belongs to Aragorn, making it a frequent but incorrect answer when several Middle-earth blades are listed together.