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)
At the risk of sounding like a basic bitch, I'm going to go with T-Rex. Sure he has ridiculously silly arms, but he gets a pass because he could bite through a car. It's a prime case of be careful who you pick on in school.