Well, there's Rose, my Clefairy, for starters - she's always especially amazed me, with how motivated she is to get stronger even though I never push her, and how large a variety of different skills she can learn.

There are Dittos, that can transform into near-perfect copies of whatever they see; Magikarps, small fish that transform into great dragons; Ponytas, horses that somehow are on fire...

[no he hasn't let go of that one yet]

And the legends that I read in the library in Ecruteak, about the three beasts who were revived by a rainbow-hued bird. They were really fascinating - I'd love to see even one of them, at least once. I mean, I think the dragon that flew through Johto that one day might have been related, but I'm not sure...

...Ah, and really, the country of Johto itself is amazing.