Heck, there are lots. But I've got to get cracking on some beasties that aren't standard fare: So far, my players' foes have been pretty well-known: A fair number of goblins, ogres, the odd troll; a specter or two; a horde of rats.
There's been magically animated plate armor: hard to crack in a straight fight but not terribly dangerous, easy to defeat once you get the knack of it, but very VERY noisy. Sort of an armed doorbell.
Hobs: I get a little squirrelly at the term "Black Hobbits" in the sample monsters listed in the 5th edition rules, (the same reason I get squirrelly about "Yassa Massa") but I do like the idea of tweaking Tolkien and villainizing halflings, at least to some degree. So yeah, I'll have villainous halflings - Hobs will do- and yeah, they'll go in nice big packs. But I'm inclined to stat them out using Peters-McAllister, at least in rough rather than go for MRs: Like all hobbits, they're puny, but they're very sturdy, and they're very nimble. They're not going to charge in and attack tooth and claw: they haven't got claws. They've got knives, for the most part, and they've got bows. And they've got stealth. Encountering Hobs in the field, the first sign of them might be a hail of arrows.
And I like the idea of a lot of them, LOTS of them, being adherents to a horrifying spider goddess - which might be a good way to add hobs to a game without coaxing the party out into the woods to be slaughtered by silent guerilla archers. "The Temple of the Patient Weaver" has a nice ring to it.
Draugr: These Norse undead appear to be the source for Tolkien's Barrow-Wight. Draugar live in the graves of important men - indeed, they are the re-animated corpses of those men. A draugr's mound emits a great light, like a large will-o-wisp or marsh gas. The graves contain burial treasures, and the draugr jealously guards them. They're very strong (STR + CON x3. )They and stink of death, though they don't exhibit rot. They can increase their size at will, though this does not change their attributes otherwise. They can rise from the grave, even through solid rock, as wisps of smoke. They attack individuals physically, crushing them, devouring their flesh, swallowing them whole. They can attack slowly at a distance by driving their victims mad, especially by entering their dreams. Animals feeding near the grave can be driven mad; even birds will drop dead flying over the grave.
Anyone approaching the grave, or sleeping nearby, must save IQ, or wake berzerk - either fighting, or running themselves to exhaustion. They can be calmed by any non-berzerk making a save on CHA.
Some draugar can shape-change or control the weather, in the immediate region; they have been known to cause (local) eclipses. (if their IQ is above 10); they will often claim to be able to see the future, and the more clever and charismatic may try to fool victims into thinking this is so. They can also cast a Curse You on their victims: one point per day per victim. Some can cause disease to villages.
They are immune to mortal weapons: they hurt, and work defensively, but will not wound them. Bare hands, sufficiently strong, will work. A party can wrestle a Draugr down barehanded if they can withstand him. If they can wrestle him into his grave, that will defeat him temporarily. The only permanent solution is to obliterate the body with fire and scatter them wide, preferably in the sea.
Anyone killed by a draugr may come back as one.