I like Bidoof. It's not my favourite and I don't ever use 'em in battle (although Bibarels make good HM slaves hurrr), but I think they're cute. :U
Anyway, back on topic. THIS IS SO HARD TO CHOOSE. DX I'm looking at the Sinnoh Dex on Bulbapedia and and and sooo many favourites. ;_; If I had to narrow it down to a measly one, I would have to say...er...gosh. This is hard. I like Garchomp because he's badass, Munchlax because he's cute, Bastidoon because Byron uses him, Weavile because Shinji uses her, Palkia because its unloved, Probopass because I also love Nosepass, Gallade because Psychic/Fighting ftw, Leafeon because it's Grass!Eevee...but the winner would have to be Turtwig, the best Grass starter since Bulbasaur. TORTERRA FTW.
Least favourite? There are like a million of these. Top of the pile is Vespiqueen though. SHE GIVES ME NIGHTMAAARES. D: And Shellos, creepy little thing. Oh, and the ~cute~ Pokémon, IE. Burmy, Glameow, Cleffa, etc. The only ~cute~ Pokémon I like are Munchlax and Mime Jr. :S