Definitely an evolution involving any Eeveelution because a normal-type like Eevee may evolve into 7 different types of pokemon, which is awesome :L
i like when missingno evolves into jigglypuff
but seriously it would have to be ...hmmm... its too hard to say...well i like driflim, it's be one of my favorites...
Chimchar to Infernape, and on that note, Tepig to Enbuoh.
A little goofy Pokemon (a fire-butt monkey, and a silly pig), evolving into two badass Pokemon based off of Journey to the West. It is nothing short of awesome. I love the story so far, being only on chapter 47 out of 100. But now that I know of that story, I can enjoy the relationship and similarities between the two even better.
I don't care that Enbuoh is fire/fighting, too. As I have said, only truly worthy and awesome Pokemon are deserving of the title. Hence, why Blaziken, Infernape, and Enbuoh are that type. Haters gonna hate~
Signature is a WIP for the moment.
For now, I have claimed: Mewtwo, Member's Card, Wide Lens, Honey Gather, and Psystrike.
Torchic to Blaziken has to be one of my favs because, come on, an annoying little chick evolving into something as badass as Blaziken is. I love especially its voice in the anime. It has that "I can kick your ass"-tone in it.
Abra to Alakazam would be another. I mean, Abra is great and Kadabra even greater, but eventually they'll become this combination of great wisdom and power... With mustache.
Then there's Magikarp to Gyarados - that should be clear without explaining.
Vibrava LOSES Attack power and gains a x4 weakness to ice...