Downplayed: Bob's sword can talk, but remains silent most of the time.
Bob's sword talks after a demon, trying to possess Bob, misses and momentarily occupies the sword instead.
The smith or wizard that made the sword intended that the sword provide advice to its user, therefore making it talk.
Bob's blaster was designed with a built-in AI designed to offer the user tactical advice in a difficult conflict situation. note Who said it had to be a sword in a fantasy setting?
Inverted: Bob's sword cancels out all noise around it, or simply renders everyone nearby temporarily mute.
Subverted: Bob and his new sword are the only ones in a scene, and we hear a mysterious voice responding to Bob as he gazes at the weapon... and then after a bit of conversation we see that Alice has been standing just off screen all along, talking.
Double Subverted: ...And as soon as Alice is done with her line, the sword goes back to talking.
Bob discovers that his new sword can talk, and is very excited until he discovers the speakers in the hilt playing the prerecorded messages.
Bob's sword has a special knack for embarrassing him.
Zig Zagged: Bob's sword talks in its first few appearances, but the writers seem to forget about this ability soon afterward... until two seasons later, when the sword returns as chatty as ever. From then on, whether or not the sword talks at all in an episode varies.
Averted: Bob has a sword, but it doesn't talk.
Enforced: The writers need someone to give Bob battle advice, but they can't find an actor willing to do the part, so they make Bob's sword talk and have an actor already with the show do its voice.
Lampshaded: "How can you talk, if you're just a metal sword? That makes no sense!" "Some things are best left unknown."
Invoked: Bob installs speakers in his sword to play some pre-recorded battle cries, hoping that it will motivate him in battle.
Exploited: Bob interrogates his sword, inquiring about its previous owners in order to get information that could help him into his quest.
Defied: When Bob goes to buy a sword from the smith, he asks that he make sure it doesn't talk.
Discussed: When Bob receives a new sword, he comments on how he wishes it could talk like in fantasy books.
Conversed: "I stopped watching the series when Bob's sword started talking. That's just silly!"
The entity trapped in Bob's sword despises its imprisonment, and spends most of its time trying to manipulate Bob into either getting himself killed or destroying the sword.
Bob suffers from schizophrenia, and believes that his sword speaks to him, becoming increasingly desperate when his friends claim not to hear these sounds.
Reconstructed: Eventually, Bob teaches the entity in his sword to accept its fate, and the two manage to work together in battle.