Bilbo Baggins’s sword in J.R.R. Tolkien’s fiction is called Sting.
Bilbo finds the blade in a troll-hoard during the journey described in The Hobbit. Gandalf takes Glamdring, while Thorin Oakenshield claims Orcrist; these three swords were made by the elves of Gondolin in the First Age.
Sting is short by the standards of human swords, but it is an effective weapon for a hobbit. Its most famous magical property is that its blade shines with a blue light when orcs are nearby.
Bilbo later gives Sting to Frodo. The sword therefore links the two hobbits across generations and remains part of Frodo’s equipment during the journey to Mordor. In Peter Jackson’s films, the blue glow makes the warning property especially visually prominent.