Having mentioned a lot of monster I like, my favorite is probably the troll.
I do like the Poul Anderson rubbery regenerating trolls with long noses of D&D. The empty, black eyes are a nice touch.
What’s not to like about them? Mechanically, they are very tough foe through the low and mid-levels, and until you have a flaming weapon, they are a logistical nightmare as you have to use fire or acid to make sure they stay down.
But my first exposure to trolls was in the D’Aulaires’ books, expecially the one all about them called “Trolls”. It has a few stories, but is more of general survey of the types of trolls they found in folklore.
Another great children’s book on trolls was written by the son of the Berenstains (best known for their Berenstains’ Bears books). I need to find a copy. Here’s the cover, which looks like a ready-to-swipe dungeon:
I also stumbled across a short picture book with three relatively famous troll stories and art that is pretty awesome:
I’ll have to find or scan some of the inside picutures. They are quite surreal.
Now that I’ve gotten totally sidetracked on troll books, another good one which collects folk tales and some of the illustrations from the late 19th/ early 20th century revival in interest in troll stories is this: