I was gonna pick Katjaa, because even though she dies in the game, I don't think, if I were her, I wouldn't have killed myself. I'd have cried, but ultimately stayed strong for Kenny. Plus, I've always wanted to be a vet, since I was about 4 years old, so that's a plus.
But I ultimately chose Christa.
Because she survives, is having a kid soon, (assuming she is one of the shadow people *debatable*) she gets to look after Clementine... and who wouldn't want to be married to Omid with THAT sense of humour?
Lee: KENNY! >:O *throws statue at wall*
Omid: ...You broke that dude's face.
If she had been an option, I'd have picked Molly, for obvious reasons. She has amazing skills, she survives well, she's clever, and she's just plain awesome.