Good call on Thornlashers. Hadn't considered them, but they've always been the bread and butter of my Druid book.
Cervere makes an appearance in most of my Nature books these days. Fast + Elusive is just so good, especially in Domination books.
I have a soft spot for Mort, the skeleton unicorn. There are few ways to "heal" the undead, so giving your skeletons effectively Regenerate 2 is pretty awesome. Reconstructs your Wall of Bones and Altar of Skulls, too. And his 4 dice + Tainted attack is scary in its own right.
Malacoda can be great in a Necromancer build, especially in Domination. He's probably the best Guard for a double-orb zone - if you can keep him from getting pushed/teleported around. You could Tanglevine/Anchor him, but then he essentially becomes a Pest, so you give up his ability to actually guard the orb or to counterstrike (but the poison still works). His biggest drawback is you have to hard-cast him at range 0, and he's slow, so he can take a while to get into position (unless you (Lesser) Teleport him to his destination).
Necropian Vampiress, Thunderrift Falcon and Naiya get honourable mentions.