When I first started playing, we used the LBBs... but in short order the 1st edition AD&D books started coming out, and pretty much our entire group bought them. This meant that everyone knew everything; all the monsters, the magic items, etc. At the time, I started thinking how much cooler it would be if there were magic items that fit my campaign world, or that had properties unknown to the players because they were not standard items.
My first attempt at creating such magic was a matched set of five polymorph potions, which happened to have long term effects we (unfortunately) never got to play through because the majority of us graduated from high school and moved away. The idea of corrupting magic was one I very much liked, and these potions had it.
The potions only allowed the imbiber to become an ogre. They were cursed though, with each potion having a cumulative 20% chance of effect. Our bard, Eisbrandfahrer, chose the potions, and after three uses, the curse hit him. Here's how it worked: Each time he took more than a certain amount of damage, he would turn into an ogre until he had a chance to de-stress (relax after combat or get out of danger). The transition healed him a few points, but upon reverting to human form, he was a little more ogre-like. I'd written out a transition page (and probably still have it somewhere) that showed, over time, increases in height and weight, increases in strength, decreases in intelligence and charisma, changes in appearance, etc., so that after a while he would BE an ogre.
As I said, we never got to play it through, but following it to it's logical end, I would have had an ogre bard in my campaign. Although I've never written them up, I've had in mind for three decades a race of ogres, more intelligent than normal and certainly wittier, who serve as bards and minstrels for other fell races.
But back to the magic, I have other items I created years ago that I'll bring up later. For now, let me point out two interesting columns at other blogs: Fr. Dave's tables for random history for magic items and Rick Stump's article about magic items that "grow" with the characters. The two mesh very well, and have me convinced (whether or not that was their combined intent) that every permanent magic item in my OD&D campaign should be unique. Of course, potions and scrolls and such won't necessarily be so, but every weapon, piece of armor or miscellaneous magic item will have a history of their own, which points to their powers.
In my son's game Friday night, my thief, Corrin Aledrinker, found a magical dagger... from the book it's a standard "+1, +2 vs. smaller than man-sized creatures" dagger. Tomorrow I'll tell you about "Ratter," a magical dagger based on this one, but with a history in my campaign world that will probably show up there at some point.
BTW, Happy Fathers' Day!