Wasn't there a thread like this a while back? Ah, no matter.

I have a fondness for the remorhaz. A polar insect thing that generates intense heat. It's not an incredibly intricate concept, but I think it's cool.

Similarly, the ankheg. Acid-spitting whack-a-mole. Always cool.

Can't really diversify these two all that much, though. Not like, say, the githyanki and githzerai. Those two races feel like they should have a whole series of novels dedicated simply to their history.