I'm a big fan of the Earthdawn take on magic items. When you find a magic item, in order to use it you need to learn some of it's history, and spend legend points (Eathdawn XP) to bind it to you.
As you learn more about it, it's name, the name of the first hero to wield it, the name of the first horror it killed, and as you recreate great deeds that it performed or atone wrongs committed with it, you can bind it further to yourself (with further legend point expenditure) and gain access to greater bonuses and powers. In this way, the item can stay with you for a significant duration, as what starts as a (in DnD terms) +1 long sword, could by the end of the players career be a +6 holy avenger (or the like).
The named artifacts in DnD4e seem to map reasonably well onto ED magic items, and it would seem that gaining concordance by doing tasks such as "slay an undead, max 1 per day" could be replaced with discovery of the item's history and the like, while the concordance chart and enhanced abilities as the concordance grows could allow for the increasing power of the item as it is bound to the character.
What is missing though is the investment by the character in that particular item.
- Having the player spend experience points on the item doesn't sit well with me, as that mucks with the "party is at the same level" assumption of the game.
- Having the player spend money on the item doesn't feel like a significant enough investment.
Does anyone have any good alternative resources that players could invest into items?