In The Lord of the Rings: The Fellowship of the Ring, Bilbo’s sword is called Sting.
Bilbo finds Sting in the Trollshaws alongside two larger Elven blades. He later gives it to Frodo before Frodo leaves the Shire. The sword is small enough to resemble a large knife to a human, but it is an appropriate sword for a hobbit. Its blade glows blue when Orcs or goblins are nearby.
Frodo carries Sting through much of the trilogy. He uses it during encounters with Orcs and in Shelob’s tunnel, where the weapon becomes an important part of his defense. The films also use Sting’s glow as a clear visual warning of approaching danger.
Sting is distinct from Glamdring, Gandalf’s sword, and Andúril, Aragorn’s reforged blade. Its earlier history connects it to the hidden Elven city of Gondolin, because it was made by Elves in the First Age.