Elemental grues are tainted elemental creatures from Complete Arcane. Their mere presence disrupts elemental magic. These creatures are prized by many wizards, for at the heart of each grue lies a pearl-like magic object, each carefully etched with the arcane workings of an elemental spell suitable for copying into a spellbook. This spell is the only thing that remains of the creature if it is slain. And now we're done with the small bestiary from Complete Arcane.
Pseudonatural creatures are creatures native to the Far Realm, the plane of insanity. They seem normal at first, but when they turn into a mass of writhing tentacles, it becomes apparent that they are not natural creatures. This template for printed in D&D 3.5 three times.
Complete Arcane for D&D 3.5 has the effigy template that can be applied to normal creatures to turn them into clockwork doubles. The sample monster is the dire lion effigy.
Complete Arcane for D&D 3.5 has elemental monoliths that are said to be more powerful than the elder elementals, but still weaker than the primal elementals. That's basically everything there is to it - it's just an intermediate power category between those two.
I found some monsters in D&D that are just animated hands or arms. Flying fingers are animated flying fists. Necromancer knuckles are the same, but with selective magic immunity. Crawling claws are animated non-flying fists. Interestingly, they are all constructs, not undead creatures. Dreads are animated skeletal arms. They are undead, not constructs.
Phaerimms are sadistic underground aberrations with innate magical abilities. They used to be very powerful on Faerun until some other mages imprisoned them in the Underdark. Even those who managed to escape imprisonment accomplished such great feats as enslaving beholder cities. Cool.