5. Grimalkin, The Shadow Dragons by James A. Owen
This cat has historical, mythical, magical and legendary secrets pouring every which way out of him. In the series (the Imaginarium Geographica), he has symbolic and physical importance, and he represents betrayal, ancient history and the most fantastic of the fantastical to the main characters. Grimalkin also spouts riddles at every turn, confounding almost everyone who speaks with him, which makes him that much more entertaining to read about.
4. The city, The Summer Prince by Alaya Dawn Johnson
The only reason the city isn't rated higher is because we don't get enough of her! Alaya Dawn Johnson's fantastic world is entwined with the city of Palmares Tres, and the city herself is sentient. She's fully aware of the divide between the poor in the verde and the rich in Tier Eight to Ten, and she's wise but distant, caring but omniscient. And when she becomes intricately tied to one of the main characters in this book, well, let's just say I had my heart broken a little.
3. Hake, Icefall by Matthew J. Kirby
Pride and brutality define Hake. His battle prowess and confidence as captain make him easy to admire, but it's when his power and vulnerability are juxtaposed that his character is completely endearing. Add in that loyalty that makes him strong from the core, and he makes for a fantastic friend too, even as he tentatively reaches out to the protagonist.
2. Taggle, Plain Kate by Erin Bow
If Taggle didn't make you laugh, snort, grin like crazy and then cry, then you have no heart. I'm serious. This cat is written more haughtily than your fourth-year English university professor and yet when it comes to Kate, he's a total softie. That juxtaposition completely won his way into my heart, and when he makes that sacrifice for Kate... ugh. Pass me the tissues.
1. Tool, The Drowned Cities by Paolo Bacigalupi
Though he makes his initial appearance in the companion prequel Ship Breaker, Tool comes into his own in The Drowned Cities—and boy does he take the stage. He wields his half-man, half-dog/cheetah/jackal/etc. status bitterly yet proudly, and his outlook on life and survival in Bacigalupi's harsh world is unflinching and effective. He's kickass, in other words, and when his vulnerable side comes out (which is nearly never), he'll make your heart melt.
(And, if you're me, he'll have you going "don't go Tool please I love you don't go don't go"—but. You know. That's just me.)