Giant hogweed (Heracleum mantegazzianum) and manchineel (Hippomane mancinella) for their toxins!
Black witch moth (Ascalapha odorata)… a big black moth with a spooky name! Some fascinating and spooky folklore to go with them too if you look into it. I had the pleasure of seeing them in Morelos.
I’m sure most people find parasitism to be at least a little spooky. Zombie ant fungus (Ophiocordyceps unilateralis), the green-banded broodsac (Leucochloridium paradoxum), and tarantula hawks (Tribe Pepsini) have attracted significant attention and notoriety for their unique behavior.
There are definitely more I can’t recall right now as I’m a bit sleepy. Might have to make a second post later!