After a certain age people stop asking you what your favorite dinosaur is, and I think that's sad.
My current one's the Anchiornis, because it's in the same clade as birds so it's in their family tree, and it really looks like a prototype of a bird. It had 4 wings for example, but it already looked very birb-y:
(Figured I'd just turn an earlier comment into an actual post because why not)
I love this question! This made me really happy. My favorite has always been (and remains) the brontosaurus. (Probably can blame "The Land Before Time" for its influence.)
I remember in the early/mid-90s being corrected that brontosaurus wasn't a dinosaur species, but was actually the same as apatosaurus. Being a stubborn child, I refused to accept this and always considered the brontosaurus, not the apatosaurus, my favorite. I felt so vindicated when the study came out in 2015 that brontosaurus and apatosaurus weren't the same.
Perhaps that's why I still stubbornly refuse to let go of Pluto: the minute hope that my favorite planet will be recognized again someday. Alas.
I had a plastic brontosaurus toy as a kid that I loved. It had a weird chemical smell to it. 30+ years later, when I hear "brontosaurus" I instantly and vividly swear I can smell it