It's really difficult to choose one, but I'd say Rattata. Yes, this one. It was the first one I caught by myself during the first time I played my first Pokémon game, and managed to bring it to level 100 and it kicked as much butt as my Charizard! So, I'd say that it's my favourite Pokémon, as it's that one terrible Lvl2 rat I caught in the high grass, almost KO'ing it with a single blow, and that I managed to fight the Pokémon League with!
... I'm getting lyrical. Right now, I'm supposed to write a report on the rentability of villas in Barcelona for my company, but I dug out my old GBA SP and all of my Pokémon game when I visited my parents' place a couple weeks ago, and I'm starting to think that these villas can wait a couple days, while maxing out a Rattata can't

Of cource, my favorite is Psyduck! Awesome

Umbreon

I’m the type of player to constantly restart my games and marathon through them. In Gen I, when I didn’t pick Squirtle, Vaporeon always made the team and was my favorite Pokèmon.

When Gen II rolled around and we got Umbreon introduced to us, I had no idea how to get one. All I knew is Karen’s in the Elite Four was a pain. Eventually the anime gave Gary Oak an Umbreon and seeing it battle made it look so sleek, so strong, so smart, and so loyal I’d fallen in love. Now I try to add Umbreon in every first-time playthrough when Eevee is available.

Well... I`ve been thinking about this for long time, and I made my decision.

1. MissingNo. (I hope this counts as a pokemon...)

2. Alolan Ninetales (It looks much better than the original.)

3. Zoura

4. Mew

5. Victini

6. Palkia

7. Dialga

8. Giratina

9. Genesect

10. Rayquaza

Least favorite...
Any SWSH pokemon.
(Except Croviknight)

My Fav's are Metagross and Charizard.