I always thought the animal that sounds most like an insult is the Disorderly-bristled Stumpy Earthworm.
A couple of birds with scientific names that are just fun to say: Rollulus rouloul (crested wood partridge) Upupa epops (hoopoe)
Bastard eel The dinosaur genus Thescelosaurus means “godlike reptile”, though the animal itself is quite small by non-avian dinosaur standards
I just discovered this thread, and is it sad if I think it might be the best thread on Zoo Chat right now? Also, I've always found the name mot-mot to be kind of funny sounding, although it gets blown out of the water by many of the other entries here.