I’m trying to recall what my weirdest magic item creation ever was back in the day but drawing a blank. I think I was pretty conservative, probably to maintain any appearance that I knew what I was doing. More recently I’ve written up (and posted here) flags, undead bird heads, masks, a conch, a fruit, and a candle snuffer among other things. The snuffer I later discovered had already been written up in AC4, more or less... of course the supplement has several kinds of snuffers to boot.
There’s more than just a couple of arguably silly items found in this book. Here's two that have accompanying illustrations… (paraphrasing)
The Barrel of MonkeysThis item both contains an albino ape as well as polymorphs anyone looking into the barrel into an albino ape. Also, albino apes will continue to pop out of the barrel every turn until there’s a hundred of the things. It’s not clear here whether they disappear back into the barrel (or into thin air) once everything and everything nearby has been torn asunder. Or maybe they go on to live fruitful lives of mindless destruction forever after. The barrel loses its power if moved, but not if you move it telepathically. Since it’s not clear where the apes go, and also not clear if when a second person looks into the barrel whether another hundred white apes appears, this thing might very well be a weapon of mass destruction.
Wheel of Burning
So what's your favorite mundane magic item that you wrote up or that your DM threw at you?