I can't choose only one, so...
In no particular order....
Awai - Someone getting excited when another player's power on? Me likey. Plus she's adorable. Professor Awai on /a/ is quite informative, too!
Sukoya - It's freaking Grand Master Kokaji Sukoya! I see a little bit of other Sakis on her, plus she's Japan's strongest and a modest person.
Yukiko - The one from Usuzan, probably the taishou and the first ever catholic mahjong idol (lol)
Other than her looks, she just sort of... hits me. Like, that! That's the person! And I have a crush of some sort to her... :P