Did Dragons, Demons, and Devils' The rest of D is cake after that. Pretty much the rest of the alphabet is going to be cake after that...
Lost world? Bluh. Alchemists. I figure dinosaurs are the alchemist's experimental animal of choice. (I tend to go for the crazy alchemist whenever the monster doesn't have any particular mythopoeic resonance but is cool anyway.) So: Up in the tower and summoning beasts from lost time periods into his pentagram and then making like the ankylosaurus have eyeballs where those bumps in its shell are supposed to be or a bipedal triceratops with a 10-foot chain where its neck's supposed to be that it swings around like a morningstar.
Speaking of crazy alchemists.... I myself personally feel like the Displacer Beast should not be taken for granted. Like it should not just be like "Oh, a displacer beast is behind that, like, tree over there." For me, this is doable because most of my players are relatively new and have no idea why a puma with tentacles would be 3 feet away from where it appears to be. Or why it's a puma with tentacles,. I can totally have this in the alchemist's basement in the cage next to the velociraptarantula and everyone will be all "Whoa, what's that?" But put it on the Random Wilderness Encounter Chart and it's just some cheap cut-and-paste thing.
Here's my problem with all genie-kind: they're top-heavy. Whether this is because I'm a professional painter or because I'm just insane is not for me to decide.
Oh my god there are too many dogs in my game already.
Fuck dolphins. A dolphin can be a ranger's animal companion according to the 3.5 PHB. Which is like saying "Your campaign can be lame if you want."
These are great, but they are kind of like snacks and PC death, in that they're really largely a logistical challenge for the DM--like you go "Oh, since so-and-so's not here she said I could just run her character like an NPC" and then--dopplegangering happens.
Dragons, et. al
A centaur that makes sense in a dungeon. Also a thing that's going to probably be the coolest mininature on anybody's tabletop.
Just as the cockatrice suffers because the medusa and basilisk do the same thing but with more style, the dryad will forever be known as the allegedly seductive female monster who appears after the (much better-looking) Succubus, and before the unillustrated (but better-named) Nymph. Anyone who would choose the Dryad with that competition is clearly playing Ren-Faire-Hippie-D&D rather than Metal D&D and I do not approve.
The forest can be creepy though, and so the dryad isn't totally hopeless--rarely mentioned in the category of "screw-your-players Save-or-Die monsters" the dryad will use-her-charm-and-take-you-away-to-the woods forever-power if: seriously threatened (ok, fine) or on any male of 16 or greater charisma. Can you blame people for using Charisma as a dump stat?
Dwarf and Dueregar
Dark dwarves never quite worked as well for me as vilians as dark elves. Elves think they're better than everyone else and dark elves are elves that think they are better than everybody despite obviously being evil. Dwarves seem basically like just methaphors for hardworking viking types and just having them be your enemy out of natural self-interest seems both more straightforward and more complex than bothering to go make them a whole race that's always bad.
Also, Dwarves are easy to sculpt at 28mm scale, so the minis usually look good.
A demilich is a skull that sits in a pile of dust in a corner and plots your doom. As totally immobile villains go I think the demilich has it all over Sauron. It's hard to to figure out what the big eye's problem is, whereas one look says what the demilich's problem is with you--you're alive, he's not, and he resents it.
It's funny how certain objects convey a message -- my washer and dryer, for example. They can't speak, of course, but whenever I pass them they remind me that I'm doing fairly well. "No more laundromat for you," they hum. My stove, a downer, tells me every day that I can't cook, and before I can defend myself my scale jumps in, shouting from the bathroom, "Well, he must be doing something. My numbers are off the charts." The skeleton has a much more limited vocabulary and says only one thing: "You are going to die."
— David Sedaris