Bug
Favourite: Scyther, it's really cool looking.
Least favourite: Metapod, it's screwed me over twice, once I found a Shiny, and I ran out of balls, and I caught one in Blue thinking it's be a quick, and easy way to Butterfree, but
NOOOOOO it had to only have Harden.
Dark
Favourite: Houndoom, it's really cool looking, and my Houndoom in Platinum is pretty good.
Least Favourite: Hmmm, Shiftry, I like them all to be honest. <_<
Dragon
Favourite: Rayquaza, it's made of win in all aspects.
Least favourite: Flygon, it's ugly, and I keep forgetting it is a Dragon type, all I know is that I can Ice Beam it to death. <_<
Electric
Favourite: Raikou, I hated hunting it down, but I love the way it looks.
Least Favourite: Pikachu, I used to love it but I'm still a little mad that it is the only thing that can use the Light Ball, also, I just love all Electric types so Pikachu kinda fell into last. I prefer Raichu, and I for some reason prefer Pichu too.
Fighting
Favourite: Oh definately Machoke, it's really neat looking, and two arms are better than four.
Least Favourite: Poliwrath, it's ugly in my opinion, I think it's the lack of a face. <_<
Fire
Favourite: Typhlosion with Entei in a close second, both are strong, and both look really cool.
Least Favourite: Magmortar, it's a little too roley-poley for my liking, especially when compared to Magmar which is my third favoruite Fire type.
Flying
Favourite: Startraptor, it looks really really cool, and I can actually spell it's name.
Least favourite: Hopip, I hate being typical, but that thing is pathetic. <_<
Ghost
Favourite: Giratina, it's really really cool looking.
Least Favourite: Shuppet? I dunno, I can't think of a Ghost type I don't like. <_<
Grass
Favourite: Torterra, it's really powerful, and my Torterra has been a great partner.
Least Favourite: I'm not going to say Hopip again, so I'll say Shroomish, I don't know why though. <_<
Ground
Favourite: Cubone, it's really cute, and so sad, he needs a hug.
Least Favourite: Trapinch, it freaks me out.
Ice
Favourite: Articuno, it's so pretty, and elegant, my favourite Legendary Bird.
Least Favourite: Purple-face Jynx, yeah, it more racially sensitive, blah blah blah, but it just doesn't look right to me.
Normal
Favourite: Zangoose, it's both cool, and powerful.
Least Favourite: Slaking, It isn't cool, and I hate it's Ability.
Poison
Favourite: Nidoking, it's good in both Special Attack, and Physical attack, it has high HP, it looks really cool, and has a great range of Attacks. It's all around great, and the backbone of my team.
Least Favourite: Gulpin, it's ugly, and turns into something even uglier.
Psychic
Favourite: Mewtwo, it's badass. 'Nuff said.
Least Favourite: Mr. Mime, it's kinda creepy. <_< >_>
Rock
Favourite: Tyrannitar, it's powerful, and cool, also with the inclusion of Aqua Tail it's pretty well rounded.
Least Favourite: Rhyperior, it was a huge disappointent.
Steel
Favourite: Scizor, it's even cooler than Scyther.
Least favourite: Magnemite, engh, I don't know why.
Water
Favourite: Guess.
Okay then, Golduck, like Nidoking it's pretty powerful with decent Speed, and HP, also a fairly large range of attacks, and it looks really neat.
Least Favourite: Feebas, it's ugly, yeah, that's the point, but it's really really ugly, plus it's evolution isn't nearly as cool as Gyarados. XD