Charles Saeger posted about smart swords in GURPS the other day. I hadn't given them much thought.
I don't use intelligent weapons very often. I handed out two swords with personality in my last game - the swords Malice and Grimslaughter* - but their personalities weren't of the talking sword type.
We had some in my AD&D days, but generally we handed out swords with special abilities but not intelligence. I think we just didn't have a handle on why and how. The only intelligent weapons I knew of were Stormbringer and the magic weapons in S2 White Plume Mountain. Not a lot to go on, and even reading Elric came years after I started gaming (during junior high, I was 4-5 years into my gaming hobby by then.)
I really should make use of them more.
GURPS has a spell to make weapons intelligent - the Weapon Spirit (VH) spell in GURPS Magic. It's an interesting spell. It doesn't take Sword X and give it Ability Package Y. It takes, instead, Character X and stuffs their knowledge into Sword Y, giving it Ability Package Z.
Mostly what you get out it is a smart weapon, but if you choose the origin spirit well, you get a smart weapon with a nice pack of skills. It is also a useful way to limit a weapon, as well - it has to react well to the bearer, so you can weed out the types you don't like.
It comes with Per 10 and it can see and hear, and should warrant a 360 degree roll to see things when held out (or peering from its hilt, depending on positioning).
But what kind of skills? Choose a fallen warrior and you could get a basket of Tactics, Strategy, Armoury, Connoisseur (Weapons), Leadership (maybe it'll act as a complimentary skill roll for you), and advantages as well - although it's not exactly clear how they'll help, some might work very well, like Luck or Danger Sense. A thief's knife could have a thief's spirit in it, and advice on Lockpicking and Traps (and spot them with its Per 10 + Traps), Streetwise, and Shadowing. Wizards may not come with spells, but maybe they will.
I feel like I haven't really taken advantage of this. I've handed out souls-in-objects, but not quite weapons with packages of skills. Maybe I need to do more of this in my DF game.
* Hopefully, they and their associated weapons, will appear in DF terms at some point.