Normal: Skitty/Delcatty. Love them both equally.
Bug: Either Scyther or Yanma. Scyther has a great design, but I liked using my Yanma in Colosseum
Fighting: Virizion, very closely followed by Mienshao and Breloom. Love all their designs. A dainty grass antelope? You bet. Weasel thing with long arm fur? Pretty neat. Dinosaur/mushroom? Heck yes.
Flying: There are A LOT of these I like, but I'll go with Mandibuzz. It's ugly in a sick, awesome kind of way.
Poison: Tie between Nidoking and Nidoqueen. Incredible design.
Water: Kabutops looks sick. For pure a Water Type then Suicune.
Fire: Either Entei or Flareon, tough choice. A Chinese guardian lion or a puffy fire catfox thing... that's tough...
Grass: So many I love... I can't even... let's go with Meganium, Sawsbuck, Tropius, Hoppip, Serperior, Leafeon, and Whimsicott. Indecisive, I know...
Rock: Tyranitar, closely followed by Golem.
Steel: Aggron with Skarmory coming close.
Ground: Flygon, even though it should be a Bug IMO
Dragon: ZEKROM ZEKROM ZEKROM ZEKROM Did I mention ZEKROM?
Electric: Manectric, extremely closely followed by Luxray. I also like Zebstrika and *gasp* ZEKROM
Psychic: Espeon, coming close is the lovely Girafarig.
Ice: Sneasel and Articuno.
Dark: Absol. DAT DESIGN
Yeah, so as you can see I have trouble picking just one favorite lololol