Iirc:
Crabs would enter a defensive stance if you got close, but wouldn't engage till you got closer.
Efts would do the same.
Goats and Dodos would follow you out of curiosity.
Marmots and Squirrels would run away if you weaponskilled near them.
Karakul would put you to sleep with sheep song.
Goat horns/crab shells/skeleton skulls/Coblyn crystals/Buffalo horns could all be broken off mid-fight, often leading to special drops (the eyepatch from skeletons being the only actual wearable gear that dropped directly from mobs in that game).
Elementals/Primals couldn't be hurt with spells of their own element.

In fact, as i recall, the giant buffalo fight involved everyone targetting his legs (through use of weaponskills that specifically target legs rather than having legs as some kind of seperate mob) until he fell to his knees, then targetting his head to break his horns, while maintaining Battle Regimens to keep his damage down.