What are people's favourite enemies, and why?
A few of mine:
Drow necromancers & priestesses introduced in MOTU, plus the harpies & satyrs in the stormhorns - ok, they're annoying to fight but the fact they necessitate a more tactical element in approaching the fight with how they work together.
Quells - moar quells for new content! Frankly we need more things that can make the mighty all-dominating divine casters cack themselves
rust monsters - their "oooo you're made of noms!" to warforged makes me smile