Well, mine are mostly one time characters so...
First off! The first Pokemon character I began to favor was Kasumi, I just liked her xD her personality, the hole bike thing. All of it =] Though I don't like her as much now, she'll still always be up there in my list of favorites. Next came Trixie, a girl who appearing during the Johto arc of the anime, she was quite older than Satoshi and Kasumi. She was really pretty and had an Azumarill, I began to like her because I developed this weird fantasy of her and Will being together, I even wrote a fanfic about it, which will never be posted anywhere xD She was just awsome, and girly, and frilly, and great.
Then came Haruka, I just liked her right of the bat, especially when she fangirled for Kasumi, I always would say how pretty Haruka was, I liked her Torchic too. I also liked her becausse she and Shuu gave us the first MAJOR shipping plots in the anime, which is delishious :3
Now here comes my all time fav character of EVER!
FRICKIN' JOE MACHEAL SHOULD STOP MAKIN' FUN OF SNOOKI SHE'S WAY BETTER THAN YOU, HE'S A LITTLE LOSER NO BODY > : (
But anyway, I'm talking about Kanata/Kelly, she's great and pretty and awsome ^.^, she's been my favorite for a while now, seeing as how her personality was so different and awsome. She's my current favorite character, and will be for a long time :]
Last but not least, Maryln, I liked how she liked cute things and I always thought of her as an otaku, who would use the words 'KYYAAA' and 'KAWAII' in every sentence, I could also see her talking in text talk all the time too...I was suprised Takeshi was annoyed by her, i've never seen him annoyed ^^;