Funny that you mentioned it. I've been working on an idea for these very same things. They're going to focus on Luck. I'm calling them Lucky Items. They can be weapons or charms, and they give temporary bonuses that can be burned. Eventually they lose their special qualities over time and use, but on some rare occasions they may become Legendary, and essentially magical enchanted items. The situation would have to be perfect for this to happen, though. And on some occassions a mundane item can become a Lucky item.
For example, imagine a sword that you find, and during the first fight you use it, you roll a 20 and take down an evil lich king. Talk about luck. If you declare it as such, maybe it is! Give it some Luck Points that can be burned over time just like regular luck. Maybe 5 or 6 levels later, towards the end of your career, it has only one luck point left, and you need to defeat some demon from out of time and space and you roll need to burn that final point to send it back to oblivion, I'd say that weapon would become Legendary.
There are details to figure out obviously. But I'm working on this idea, and it'll be found in Issue 2 of my zine!
I like it. Very much like historical "magical" items were thought as such. Think of the spear of longinus, Charlemagne's sword, etc. I must think on this.