Bug: Heracross - I've always liked this guy and his slick, but kinda silly look. And the fact that he's really strong doesn't hurt.
Dark: Houndoom - I'm not a huge fan of any Dark type pokemon now a days, but I remember that as a kid I really liked this hellish dog.
Dragon: Vibrava - Most people probably doesn't think of Vibrava when they think of dragon pokemons, but I love him Vibrava. I'm probably the only one that prefers him over Flygon.
Electric: Ampharos - Not much to say besides that I like him.
Fighting: Hitmonlee - Coolest fighting pokemon by far! But to be honest, if I hadn't picked Heracross for bug then he would be here instead of Hitmonlee.
Fire: Magby - Love him! He's so cute. I use him as my egg hatcher just to have a reason to use him.
Flying: Zubat - Really annoying at times, but I love it's design and it's a fun pokemon to use.
Ghost: Golurk - My favorite animated movie is The Iron Giant and Golurk always reminds me of it. I also find the design to be very elegant and the unique type combination is one that I think is really cool.
Grass: Exeggutor - He's so silly and happy! What's not to love? Cool typing as well.
Ground: Sandshrew - Cute and brilliant design. This is one of the most well designed pokemon to date in my opinion (Looking forward for his igloo version).
Ice: Lapras - Beautiful and pretty realistic. It's fun to use as well.
Normal: Ditto - Happy slime = Me likey
Poison: Nidoking - Always liked this monster looking guy. I like how it's poison-type without screaming "poison" or being based on something that isn't venomous or smelly. I like Koffing and Garbodor as well, but I think pokemon need more designs like this.
Psychic: Hypno - Spooky and weird. I've never been one to like the best/strongest pokemon. So in gen 1 I never wanted Alakazam, I wanted this guy.
Rock: Sudowoodo - A happy wannabe tree that is a pure rock and is an homage of Snorlax in gen 2. I don't know how someone couldn't like him.
Steel: Magneton - Not really sure why I like him so much. His design is kinda boring, but it works for him since he's made of magnets. I think it's his typing and that he's fun to use that makes me like him.Water: Tentacruel - I like a lot of water type pokemon, but Tentacruel is special. He got a cool and distinct design, he looks dangerous so you know that you shouldn't mess with him and he's a really good pokemon to have on your team. His typing work really well with his bulk. Love him! Tentacool was also the first shiny I found in the wild, so I now have a shiny Tentacruel which is one of the best looking shinies in my opinion.