Oh, carp.
First off, this sounds more like a modding thing than an adventure mode thing...
Second, I have far too many to post here. I'm working on a God of War mod, with civs that have multiple types of creatures (using castes), and each of those races has at least ten different creatures, from minotaurs to harpies to cyclopes... Then, I have ElfSlaves... the females are milkable, the males are shearable, and I quit playing with them because I actually started to feel like a horrible person. Then, Scythods, which are part of the Spearbreakers II mod - aliens shaped roughly like praying mantids with spikes for legs and scythes for arms, and no eyes... Manamaids, which are absolute horrors to behold, repugnant, disgusting, corpulent crosses between manatees and inordinately obese women, mermaid style. They wear pr0n costumes and are capable of "busting a sexy move", which causes everyone nearby to pass out in horror. (Also the SB II mod.) I've made skywhales (the ultimate bane to any demon (imagine something the size of a football stadium floating down from the sky to crush you))... "bob-ombs" that explode when they get close to an enemy, spraying fire, oil, and shrapnel everywhere... A ton of different things from SCP (before I realized Putnam already had a mod), annnnnnnddddddd... cavy warriors. That's about all I can think of off the top of my head - at least as far as entities go. Besides flying dragons - totally not a good idea.