Check out the upgradable Sword, below.

A Fighter in one of my campaigns developed a detailed family history.  She belonged to an ancient royal line long thought dead.  To reward this extra work on the character, I added an item to an early treasure find – an Admantium Greatsword +1.  This sword was once part of the ‘Crown Jewels’ of a fallen Kingdom – a hugely powerful relic with a long history and personal value to the character.  Now, for a low-level Fighter this was an excellent find!  However, I knew that within a few levels a +1 Greatsword would start to pale compared to new treasures that would come available.

So, I added something not in the rules, but I liked it rather a lot.  The sword had once contained five jewels of great value – rubies I think.  When the Kingdom had fallen the sword had lost, the jewels removed from their mountings, and sold off seperately.  The sword itself had fallen into the heroine’s hands, but the gems were all missing.  From time to time, she would find a hint or clue for another gem.  As she recovered them, and mounted them back to the sword, it began to gain more abilities.  Flaming Blade, upgrade to +2, etc.  By the time she’d become a high level Fighter and recovered all the gems, she had a powerful, ancient sword with great history and abilities to match hers.

That worked, and the player was quite pleased with her specialized loot.  Something similar could easily be done with armor, or spellbooks, or what have you.