I have had an interesting history with unique items, as I'm sure Ironsides will attest to if he finds this thread.
My first was Ucdauh's Ring of Leadership, and since my character was a General of Minas Ithil at the time, it was his prize possession. He credited his success to the ring, and then at one point a dirty viking beat the advy who had repaired the item and was bringing it back. Then a battle occurred in the region, and Minas Ithil stomped Norland, and a fellow noble who foraged the battlefield found the item and gave it back to Raziel.
Lately my prized item has been on dwilight. It was stolen from a Morekian infiltrator who cried rape after being tortured and robbed, and then given to my char. It used to give a 9% boost to spell casting, but an advy recently improved it to 13%