Are there any magic items that are unique to one version of D&D (only appeared in one of the following: OD&D, Holmes, AD&D 1E, BX, BECMI/RC, AD&D 2E, D&D 3E, D&D 4E, or a clone like C&C, LL, S&W, OSRIC, LotFP: WFRPOHMYGODHOWLONGCANTHISACRONYMGET*, etc.) that you feel like you couldn't run the game without?
Holmes' weird scrolls? Something from UA that didn't ever appear again? One of Frank's from the Companion Set? Something from a module or supplement? Something someone added to a clone that you now wish the game had had all along?
Basically, is there any item that you feel is so iconic that D&D wouldn't be the same without it, but it only appears in one set (as far as you know, anyway).
Or if there's a monster or spell, or something similar, go ahead and share that, too.
And shoot the hostage.
With a nuke.
It's the only way to be sure.
*Just kidding, Raggi!