I am awful at favorites so I'm giving myself three answers!
Favorite Dino in Paleo Pines: Dimetrodon
It should probably be Iris, my Kentrosaurus but right now, while working on this answer, I am in love with this little guy who follows me around cheering me on every time I pick berries off a bush. Technically not a dinosaur, but it's in the dinos game so I'll let this non-mammalian synapsid pass as an answer.
Favorite Not-Dinosaur: Ichthyosaur
Almost went with plesiosaurs because who isn't entranced by their absurd necks? But something about ichthyosaurs' big eyes and no-neck bullet shape lives rent-free in my head. Oh, and the snoots! Love the snoots. Cetaceans allegedly did it better & later, but these guys are winners in my heart.
Favorite Dinosaur, Mandatory Childhood Version: Parasaurolophus
When I was but a little larva I got asked what my favorite dino was, but of course in a way that involved silly rules about nobody else being able to pick the same one. Even my mom got in on it (Iguanodon for her). Anyways the NOGGINS on these guys... who could ask for anything else? They remain my favorite hadrosaur because nothing can surpass that tuba.