The creation of intelligent magical weapons is not an exact science and there are occasional failures, as such think of causing a little more stress to your players by "rewarding" them with an insane magical weapon
Agrophobic, refuses to come out of the scabbard without a strength check to draw it.
Haemaphobic: afraid of blood, fight at a penalty against any blooded creatures but really good against undead, elementals etc
Schizophrenic, not just one mind in your sword, lets have half a dozen minds in there, all different and bound to cause confusion
the possibilities are endless
"...the Ilthian mountains. A craggie masse of rock rysing from the Ilth'n plaines. The waters whych springe from it are ful of godeness and fortyfie those who drynk them [+1 STR]. Alas the vyle beasts resydent in these hills also bathe in these waters, and in the doing gain great strength. Foes mortallie wounded have bene known to flee, onlie to return, revytalised houres later..." - Chronicler Eamusil, Mondopedia, Vol XV (The Lands of Sylmen)