In the same vein as my Four Items posts, here are four D&D/AD&D monsters I never used. I've used monsters from the littlest Mites and Giants Rats all the way up to arch devils (one PC slew Moloch) and demon lords (Demogorgon has shown up in multiple games of mine, even before I got this cool mini.)
This was a tough four to assemble, because I have run so many, many modules over the lifetime of my D&D, AD&D, and D&D-inspired games. So even the strangest monsters show up somewhere, and if they were there to encounter, I'm not counting them as "never."
But here are four I noticed I never did get around to using:
Morkoth - a squiddly dude that lives in spiraling tunnels under water. Tough to even find a way to use something like that, I expect. I don't know if one appears in any adventure, but I never actually had one in play. I still can't quite figure out how I'd use one. I've used a lot of underwater creatures, and played some adventures set almost fully underwater (U3, for example), but never did find a use for this guy. The whole setup for it - underwater tunnels - made it seem especially specific in its needed placement, and thus really hard to use.
Slithering Tracker - The Ecology article about these made them seem pretty nasty, but it came a bit late. It's a pretty lethal-sounding thing, though, and it deserves a long, hard look for my GURPS Dungeon Fantasy game. I bet the lack of a picture, and the pace of my early games, kept this off my use list. No picture, no inspiration. And it was rare in my games for people to be camping out in a dungeon, or even resting (you just marched around fighting!) so when would one of these guys have come into play?
Son of Kyuss - I love these things, but yeah, never used them. They have all the hallmarks of my kind of play - kinda gross, kind of nasty, dangerous, with a crazy attack that makes them more than just hunks of HP. But I haven't used them . . . yet. I may need to fix that, too. This isn't an especially popular monster (although one appears in Night Arrant) with the name filed off. But it's so me that it strikes me as odd that one never made it in to any of my games.
Modrons - I think these guys have some cool potential, and I loved the modron in Planescape: Torment, but I never found a way to fit them into games. Cool but so odd they seemed to demand some special use, and I never got my head around such a special use. Perhaps if I'd run Planescape, or if they'd appeared in some module somewhere, but they always just seemed interesting without a hook I could grab on to. It's not like evil wizards summon up a modron to help kick your butt.
There are other monsters - oddball MM2 and FF ones, some aquatic types, etc. - that I didn't use. But the above four are all very interesting (or in case of the Morkoth, quite old) yet somehow never found their way into my games.
I rarely used dragons, saving them for high-level play that rarely arrived and comprised only a small portion of play time. But I did use them, so they don't get on this list. Still, I should do a post on "don't back load the fun by saving dragons until never" sometime, too.