Yeah, there was a similar topic - they are now merged.
I'd probably pick either Clapper's Cavern or Animal Antics - most likely the latter. I love the variety and the challenge of AA, but I'm also a sucker for the run, jump, duck, slide obstacle course of CC... oh and Slime Climb gets an honorary mention because of how cool (and terrifying!) it is; scampering up the mainbraces and rigging of a sinking ship in a bid to escape a ravenous and relentless piranha... I'd say this is probably my most 'feared' level from my childhood, so its memory stays with me.
Oh, and all of the enchanted forest levels are amazing for atmosphere, I agree.
Yeah, I'm really bad at picking just one favourite level.