Misty (Kasumi in the Japanese).
She is my favourite character, my favourite gym leader, and she trains one of my favourite Pokemon types - Water.
She's also pretty unpredictable. You know, you'd expect a water trainer to be all cool and calm, and then Misty turns around and has a screaming match with Ash because he's messed up...again. <3
I was always very sad that Misty was the 2nd Gym Leader, and that she was so easy to defeat. T_T Although G/S/C made her tougher =]
Seriously. I love her. She's my favourite character ever from the Series, and pretty much any Anime.
She makes May & Dawn look all prissy and girly.
The older series of the Kanto/Orange Islands/Johto are the bestm IMO.
And when Misty leaves Ash & Brock...I cry. I'm really peeved that Misty isn't in the series anymore.
BRING HER BACK NINTENDO!!!! T_T
I also named one of my dogs after her. <33
And here's the video for it, too:
https://www.youtube.com/watch?v=9ZOblRFfeDA
<3