Grass = Bulbasaur. It's my favourite starter in general. I like it because others often pick Charmander or Squirtle, and I've just felt like it was the underdog, something I've related to. It's also pretty cute, and can become really effective in combat.
Fire = Braixen. Honestly it was a though call. I almost placed Ho-Oh, but then again, not that big of fan of Legendaries, both in game, and as favourites. Braixen more because it's a cool design, and I like it's typing. I never evolve it to Delphox tho. Just if I have to complete the "living dex".
Water = Poliwhirl. I just think it's really cute. It's something about the colour, it's nature, and how it fights. Just liked him for many years, really. Also I know he is in the manga, which is cool.
Normal = Tauros. My all-time favourite Pokémon, no doubt. Growing up with a temperamentive dissorder as a kid, I felt that Tauros who had a wild temper in game and in the anime was quite reflective, that, once tamed, they can be great resources, and powerful teammates. I felt like I had the will, and power of a Tauros. So, it gave some meaning.
Electric - Galavantula. When I first saw it I thought it was really cute, and then captured it, played with it, and figured out how effective it could be on my team during B-W2.
Psychic - Gardevoir. Despite all fan-art out there, this Pokémon does have a lot of great moves in game. While I hate training up a Ralts, I still enjoy it from Kirlia to Gardevoir, often being a very strong member of any team I use when it's in the party.
Fighting = Lucario. Hard to pick out a fighting type. I guess because of Smash I thought Lucario looked pretty epic. He is sort of a face in Pokémon, and that does have it's prize, I guess.
Rock = Archeops. Honestly, it's really powerful. Rock and Flight was a delight of a combination. It's cool, and I enjoy using it.
Ground = Hippodown. I thought it was a cool design once I saw it in Diamond & Pearl. I'm more fan of the Female version, where it's all black.
Flight = Murkrow. Perhaps also one of my all-time favourite Pokémon. While mischevious, it's also a loner, growing up a victim of bullying, I also often could relate as a loner. This made me, like with Tauros feel something for the bird, and I came to like it. (Yeah, I know, getting personal here, ahaha ... don't read too much into it.)
Bug = Like with Tauros, it was ill tempered in the Anime, which was one thing, but it was still so cute. Whenever I got him in the games, I always trained him high, and used Twineedle, as it's such a powerful move. Made a real great member of any team.
Poison = Seviper. It's design is really cool, and it has become one of my all-time favourite Pokémon. It got great Poison moves, and was an effective team member.
Dark = Spiritomb. I just think it looks pretty epic, and it was obscure in it's original game, which made it even more intriguing to find it, and use it in the games. Also, the whole "forbidden" Pokémon lore makes it even more epic. Reminds me a bit of Dhelmise from Sun & Moon which I also really like.
Ghost = Haunter. Might be because it was so frustrating or time consuming to get Gengar as a child, but I really like Haunter, it's more of a Ghost than anything, and using it in my game I'd spam "Hypnosis + Dream Eater" and became a killer on the road.
Ice = Walrain. Not an easy type to pick one out from. I do think he is mighty powerful, and that Spheal is cute. Not a sucker for Sealeo tho, therefore Walrain triumphs.
Steel = Metagross. Another not easy pick. While that's said, I still thought he was awesome. Remember using one in Emerald. He was badass, pluss he reminds me for some reason by the crane in the Brave Little Toaster, ahaha.
Dragon = Hydraigon. I do not really like Dragons too much. I think they are overpowered. Still, there is something about this dangerous creature that really makes me go; "Wow", and while he takes a long time of grinding to evolve, I still think it is worth it.
Fairy = Mimikyu. I honestly don't have much other options. I still think Mimikyu's design is interesting, and he was a fun new Pokémon for Sun and Moon.