I have two rather humorous stories about sentient weapons:
One was with the High School RPG group, one of my friends playing a barbarian found a very powerful sword. But the swords EGO and Willpower were greater than that of the character trying to wield it, so it would not cooperate with him. In fact the sword felt insulted to be owned by a dirty uncouth barbarian. This caused many ‘laugh out loud’ moments when my friend tried desperately to get his sword to help during dire moments, only to have it insult him and find ways to twist his commands to its own advantage and amusement. It all came to an end one day when he attempted to intimidate a group of Kobolds, he drew the sword with a flourish. He held high the glowing sword and dramatically shouted “Destroy!” I could not resist… He knew he had done something wrong by the look on my face. His eyes went wide, “What happened?” I smiled, “It blew up.”
“What?”
“You gave it an out.”
“Huh?”
“It would rather cease to exist than be held by you.”
“Ah, dude come on…”
“Your command gave it a way to do that without directly disobeying you.”
“Fuck.”
DESTROY! Became a running joke for months.
About 10 years later with another group almost the same thing happened-
A friend of mine had a big brutish Viking character who stumbles upon a very powerful sword. Once again the sword had a greater EGO, Willpower and INT than the would be owner. And the alignment of the sword and attempted owner also conflicted. The sword was not only intelligent but it was also telepathic, the original intent was that the sword could be used as an alarm if you were sleeping and an assassin crept into your room; but you could also plant the sword in a room and use it as a spy. But in this case it meant that the sword could harass you telepathically even if you stuffed it in a bag of holding, I heckled the poor guy during the games as the ‘voice of the sword’ to which the guy would often lose his cool and shout curses and tell it to “shut the fuck up”, to which the rest of the group would look at him strangely because of course the characters could not hear anything, the insults were sent telepathically.
The sword would suddenly glow at inappropriate times giving away the Viking’s position. If he tried to use it against a ‘good’ aligned character it would grow so heavy he could not hold it. He finally got so fed up with it one night he hurled it into a lake in a violent fit of frustration, the irony of that was not lost on the fellow gamers. They looked at me expectantly but I smirked and shook my head, “No, no… I does not become that sword.”
For me gaming is not about treasure and leveling up, it is about the interaction between characters and losing yourselves in the adventure. I do everything I can to prompt and encourage the players to be ‘in character’ when talking amongst themselves, and with NPC’s.