Four is my favorite number, which is why this is four not five.
What are the four magic items you've never, ever handed out in a game? Not "I put one in, but no one found it" but just "no, no, no, not in my game."
Rod of Lordly Might - never put one in. I still don't quite get the appeal of a Swiss Army Rod that is all sorts of magic weapons at once, plus acts as a battering ram. It's just too odd, to me - it doesn't lack for uniqueness but it sure lacks in appeal to me. It feels like a truly weird item thrown in to get a laugh out of players at the expense of that guy they know who surely inspired it.
Hammer of Thunderbolts - too many stipulations on what you need to use this, plus all sorts of stackable powers if you did have the 6' in height, Girdle of Storm Giant Strength, Gauntlets of Ogre Power, etc. to use it. Basically, too restricted followed by too powerful once you unleashed the restrictions. There was no happy medium.
Sword +5, Holy Avenger - the paladin we had, the one real paladin we had - was a Unearthed Arcana-era one and I gave him a Broadsword of Intercession (from Dragon #91, I think), instead, which let him use his Paladin powers but not get quite such a powerful weapon so early. It felt like too much, and so a truly great weapon like this never quite appeared. I can't really say why - maybe just because +5 seemed so incredible that it was something that only fit with high-level play, and so I essentially pushed it off to the end like dessert but never quite got there.
Helm of Brilliance - too much, just too much. Like the Rod of Lordly Might, it seemed like a crazy gimme item that couldn't settle on what it was. I do think it's a lot cooler when I look at it now, but still, I have a hard time seeing me putting something like this in a dungeon early enough to matter in any campaign. It's another item, though, like the Rod of Lordly Might that just seems like a grab-bag of powers.
There are others I never used, of course. I can't remember a single magical Scarab of anything in my games, or gave anyone a Sphere of Annihilation (not sure I knew what it was really good for, except as a trap), or Instrument of the Bards (only a tiny handful of bards in my games.) I don't think Daern's Instant Fortress showed up in a game, or a Ring of Boccob or an Apparatus of Kwalish or a Cubic Gate. No Anything Swords, either, or Swords of Sharpness. The one vorpal blade anyone got was from a Gygax module. I only ever handed out one Cube of Force that I remember. The sole Ring of Spell Turning I remember I didn't give out but it came with an NPC. The Staff of the Magi showed up twice (once providing a memorable end to Q1 in the form of a retributive strike to destroy Lolth.)
But some stick out as ones I made a conscious decision to not hand out or make available, or shied away from. And there are ones I handed out like free candy - which is another post in an of itself.
What are your four? If you blog on it, let me know and I'll link it here!